CVE-2026-56811

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-56811", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-06-23T12:29:02.507Z", "datePublished": "2026-07-07T15:09:57.581Z", "dateUpdated": "2026-09-24T21:28:45.227Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Phoenix.Socket'"], "packageName": "phoenix", "packageURL": "pkg:hex/phoenix", "product": "phoenix", "programFiles": ["lib/phoenix/socket.ex"], "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "versions": [{"lessThan": "1.5.15", "status": "affected", "version": "0.11.0", "versionType": "semver"}, {"lessThan": "1.6.17", "status": "affected", "version": "1.6.0-rc.0", "versionType": "semver"}, {"lessThan": "1.7.24", "status": "affected", "version": "1.7.0-rc.0", "versionType": "semver"}, {"lessThan": "1.8.9", "status": "affected", "version": "1.8.0-rc.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Phoenix.Socket'"], "packageName": "phoenixframework/phoenix", "packageURL": "pkg:github/phoenixframework/phoenix", "product": "phoenix", "programFiles": ["lib/phoenix/socket.ex"], "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "versions": [{"changes": [{"at": "c498ba8cf49f6accbbd0c643a5340b58db891218", "status": "unaffected"}, {"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e", "status": "unaffected"}, {"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1", "status": "unaffected"}, {"at": "16e295d2fccab185d1292322e2bee5d46c725c8a", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "14a297e88023cb280a577962a49a0bbdeef9f4eb", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send <code>phx_join</code> messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.</p>"}, {"base64": false, "type": "text/markdown", "value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send `phx_join` messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."}], "value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send phx_join messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.5.15", "versionStartIncluding": "0.11.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.6.17", "versionStartIncluding": "1.6.0-rc.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.7.24", "versionStartIncluding": "1.7.0-rc.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.8.9", "versionStartIncluding": "1.8.0-rc.0", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "Steffen Deusch"}, {"lang": "en", "type": "analyst", "value": "Jonatan M\u00e4nnchen / EEF"}, {"lang": "en", "type": "analyst", "value": "Jos\u00e9 Valim"}], "datePublic": "2026-07-07T15:09:57.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (<code>Phoenix.Socket</code> module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).</p>\n<p>This vulnerability is associated with program files <code>lib/phoenix/socket.ex</code> and program routine <code>'Elixir.Phoenix.Socket':handle_in/4</code>.</p>\n<p>Phoenix transports do not limit the number of channels that a single transport process may join. Every <code>phx_join</code> message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of <code>phx_join</code> messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.</p>\n<p>The fix adds a <code>:max_channels_per_transport</code> option (default <code>100</code>) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.</p>\n<p>This issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.</p>"}, {"base64": false, "type": "text/markdown", "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (`Phoenix.Socket` module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files `lib/phoenix/socket.ex` and program routine `'Elixir.Phoenix.Socket':handle_in/4`.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every `phx_join` message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of `phx_join` messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a `:max_channels_per_transport` option (default `100`) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9."}], "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine 'Elixir.Phoenix.Socket':handle_in/4.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 8.7, "baseSeverity": "HIGH", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-770", "description": "CWE-770 Allocation of Resources Without Limits or Throttling", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-24T21:28:45.227Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"}, {"name": "EEF CNA record for CVE-2026-56811", "tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-56811.html"}, {"name": "OSV record EEF-CVE-2026-56811", "tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"}, {"name": "Introducing commit 14a297e in phoenixframework/phoenix", "tags": ["related"], "url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb"}, {"name": "Fix commit c498ba8 in phoenixframework/phoenix", "tags": ["patch"], "url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"}, {"name": "Fix commit d19ca0a in phoenixframework/phoenix", "tags": ["patch"], "url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"}, {"name": "Fix commit a612100 in phoenixframework/phoenix", "tags": ["patch"], "url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"}, {"name": "Fix commit 16e295d in phoenixframework/phoenix", "tags": ["patch"], "url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"}], "source": {"discovery": "EXTERNAL"}, "title": "Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove <code>longpoll: true</code> from the <code>socket</code> declaration where the LongPoll transport is not required). Lowering the BEAM <code>+P</code> maximum process limit does not prevent the exhaustion and can make it easier to trigger.</p>"}, {"base64": false, "type": "text/markdown", "value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove `longpoll: true` from the `socket` declaration where the LongPoll transport is not required). Lowering the BEAM `+P` maximum process limit does not prevent the exhaustion and can make it easier to trigger."}], "value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove longpoll: true from the socket declaration where the LongPoll transport is not required). Lowering the BEAM +P maximum process limit does not prevent the exhaustion and can make it easier to trigger."}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-07-07T16:12:27.662417Z", "id": "CVE-2026-56811", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-07T16:12:37.299Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-56811", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-07-07T16:12:27.662417Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-07T16:12:32.451Z"}}], "cna": {"title": "Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "Steffen Deusch"}, {"lang": "en", "type": "analyst", "value": "Jonatan M\u00e4nnchen / EEF"}, {"lang": "en", "type": "analyst", "value": "Jos\u00e9 Valim"}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 8.7, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "HIGH", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "modules": ["'Elixir.Phoenix.Socket'"], "product": "phoenix", "versions": [{"status": "affected", "version": "0.11.0", "lessThan": "1.5.15", "versionType": "semver"}, {"status": "affected", "version": "1.6.0-rc.0", "lessThan": "1.6.17", "versionType": "semver"}, {"status": "affected", "version": "1.7.0-rc.0", "lessThan": "1.7.24", "versionType": "semver"}, {"status": "affected", "version": "1.8.0-rc.0", "lessThan": "1.8.9", "versionType": "semver"}], "packageURL": "pkg:hex/phoenix", "packageName": "phoenix", "programFiles": ["lib/phoenix/socket.ex"], "collectionURL": "https://repo.hex.pm", "defaultStatus": "unaffected", "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}]}, {"cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "modules": ["'Elixir.Phoenix.Socket'"], "product": "phoenix", "versions": [{"status": "affected", "changes": [{"at": "c498ba8cf49f6accbbd0c643a5340b58db891218", "status": "unaffected"}, {"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e", "status": "unaffected"}, {"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1", "status": "unaffected"}, {"at": "16e295d2fccab185d1292322e2bee5d46c725c8a", "status": "unaffected"}], "version": "14a297e88023cb280a577962a49a0bbdeef9f4eb", "lessThan": "*", "versionType": "git"}], "packageURL": "pkg:github/phoenixframework/phoenix", "packageName": "phoenixframework/phoenix", "programFiles": ["lib/phoenix/socket.ex"], "collectionURL": "https://github.com", "defaultStatus": "unaffected", "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}]}], "datePublic": "2026-07-07T15:09:57.000Z", "references": [{"url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w", "tags": ["vendor-advisory", "related"]}, {"url": "https://cna.erlef.org/cves/CVE-2026-56811.html", "name": "EEF CNA record for CVE-2026-56811", "tags": ["related"]}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811", "name": "OSV record EEF-CVE-2026-56811", "tags": ["related"]}, {"url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb", "name": "Introducing commit 14a297e in phoenixframework/phoenix", "tags": ["related"]}, {"url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218", "name": "Fix commit c498ba8 in phoenixframework/phoenix", "tags": ["patch"]}, {"url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e", "name": "Fix commit d19ca0a in phoenixframework/phoenix", "tags": ["patch"]}, {"url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1", "name": "Fix commit a612100 in phoenixframework/phoenix", "tags": ["patch"]}, {"url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a", "name": "Fix commit 16e295d in phoenixframework/phoenix", "tags": ["patch"]}], "workarounds": [{"lang": "en", "value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove longpoll: true from the socket declaration where the LongPoll transport is not required). Lowering the BEAM +P maximum process limit does not prevent the exhaustion and can make it easier to trigger.", "supportingMedia": [{"type": "text/html", "value": "<p>Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove <code>longpoll: true</code> from the <code>socket</code> declaration where the LongPoll transport is not required). Lowering the BEAM <code>+P</code> maximum process limit does not prevent the exhaustion and can make it easier to trigger.</p>", "base64": false}, {"type": "text/markdown", "value": "Front the socket endpoint with a reverse proxy that limits the number and rate of channel-join frames per connection, or disable transports that are not needed (for example remove `longpoll: true` from the `socket` declaration where the LongPoll transport is not required). Lowering the BEAM `+P` maximum process limit does not prevent the exhaustion and can make it easier to trigger.", "base64": false}]}], "descriptions": [{"lang": "en", "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine 'Elixir.Phoenix.Socket':handle_in/4.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.", "supportingMedia": [{"type": "text/html", "value": "<p>Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (<code>Phoenix.Socket</code> module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).</p>\n<p>This vulnerability is associated with program files <code>lib/phoenix/socket.ex</code> and program routine <code>'Elixir.Phoenix.Socket':handle_in/4</code>.</p>\n<p>Phoenix transports do not limit the number of channels that a single transport process may join. Every <code>phx_join</code> message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of <code>phx_join</code> messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.</p>\n<p>The fix adds a <code>:max_channels_per_transport</code> option (default <code>100</code>) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.</p>\n<p>This issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.</p>", "base64": false}, {"type": "text/markdown", "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (`Phoenix.Socket` module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files `lib/phoenix/socket.ex` and program routine `'Elixir.Phoenix.Socket':handle_in/4`.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every `phx_join` message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of `phx_join` messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a `:max_channels_per_transport` option (default `100`) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-770", "description": "CWE-770 Allocation of Resources Without Limits or Throttling"}]}], "configurations": [{"lang": "en", "value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send phx_join messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.", "supportingMedia": [{"type": "text/html", "value": "<p>The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send <code>phx_join</code> messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.</p>", "base64": false}, {"type": "text/markdown", "value": "The application must mount a Phoenix socket that defines channels and expose it over HTTP so that a client can reach a channel transport (WebSocket or LongPoll) and send `phx_join` messages. The WebSocket transport is enabled by default on a mounted socket, while the LongPoll transport is opt-in. Applications that do not mount a socket with channels are not affected.", "base64": false}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.5.15", "versionStartIncluding": "0.11.0"}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.6.17", "versionStartIncluding": "1.6.0-rc.0"}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.7.24", "versionStartIncluding": "1.7.0-rc.0"}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "1.8.9", "versionStartIncluding": "1.8.0-rc.0"}], "operator": "OR"}], "operator": "AND"}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-24T21:28:45.227Z"}}}, "cveMetadata": {"cveId": "CVE-2026-56811", "state": "PUBLISHED", "dateUpdated": "2026-09-24T21:28:45.227Z", "dateReserved": "2026-06-23T12:29:02.507Z", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "datePublished": "2026-07-07T15:09:57.581Z", "assignerShortName": "EEF"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Phoenix.Socket'"], "packageName": "phoenix", "packageURL": "pkg:hex/phoenix", "product": "phoenix", "programFiles": ["lib/phoenix/socket.ex"], "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "versions": [{"lessThan": "1.5.15", "status": "affected", "version": "0.11.0", "versionType": "semver"}, {"lessThan": "1.6.17", "status": "affected", "version": "1.6.0-rc.0", "versionType": "semver"}, {"lessThan": "1.7.24", "status": "affected", "version": "1.7.0-rc.0", "versionType": "semver"}, {"lessThan": "1.8.9", "status": "affected", "version": "1.8.0-rc.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Phoenix.Socket'"], "packageName": "phoenixframework/phoenix", "packageURL": "pkg:github/phoenixframework/phoenix", "product": "phoenix", "programFiles": ["lib/phoenix/socket.ex"], "programRoutines": [{"name": "'Elixir.Phoenix.Socket':handle_in/4"}], "repo": "https://github.com/phoenixframework/phoenix", "vendor": "phoenixframework", "versions": [{"changes": [{"at": "c498ba8cf49f6accbbd0c643a5340b58db891218", "status": "unaffected"}, {"at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e", "status": "unaffected"}, {"at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1", "status": "unaffected"}, {"at": "16e295d2fccab185d1292322e2bee5d46c725c8a", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "14a297e88023cb280a577962a49a0bbdeef9f4eb", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "matchCriteriaId": "3CF8EA55-C063-4742-87ED-53E1998977B5", "versionEndExcluding": "1.5.15", "versionStartIncluding": "1.2.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "matchCriteriaId": "809E49A8-D727-4E05-BBF9-F9E34077E4A4", "versionEndExcluding": "1.6.17", "versionStartIncluding": "1.6.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "matchCriteriaId": "3257C901-8FC3-4107-95C6-C57F909FFE40", "versionEndExcluding": "1.7.24", "versionStartIncluding": "1.7.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*", "matchCriteriaId": "8F98C1AC-1593-43EB-929A-4D3B7597C9BC", "versionEndExcluding": "1.8.9", "versionStartIncluding": "1.8.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine 'Elixir.Phoenix.Socket':handle_in/4.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9."}, {"lang": "es", "value": "La vulnerabilidad de asignaci\u00f3n de recursos sin l\u00edmites ni estrangulamiento en phoenixframework phoenix (m\u00f3dulo Phoenix.Socket) permite a un atacante no autenticado causar una denegaci\u00f3n de servicio contra cualquier punto final que monte un socket Phoenix con un transporte de canal accesible (WebSocket o LongPoll).\n\nEsta vulnerabilidad est\u00e1 asociada con los archivos de programa lib/phoenix/socket.ex y la rutina de programa \u2019Elixir.Phoenix.Socket\u2019:handle_in/4.\n\nLos transportes de Phoenix no limitan el n\u00famero de canales a los que puede unirse un \u00fanico proceso de transporte. Cada mensaje phx_join que un cliente env\u00eda a trav\u00e9s de una conexi\u00f3n inicia un proceso de canal persistente, y el proceso de socket acepta un n\u00famero ilimitado de ellos. Por lo tanto, un \u00fanico cliente no autenticado puede abrir una conexi\u00f3n WebSocket o LongPoll y transmitir un gran n\u00famero de mensajes phx_join, generando cientos de miles de procesos de canal a trav\u00e9s de esa \u00fanica conexi\u00f3n y finalmente alcanzando el l\u00edmite m\u00e1ximo de procesos de BEAM. Una vez que la tabla de procesos se agota, la m\u00e1quina virtual ya no puede iniciar nuevos procesos, denegando el servicio al tr\u00e1fico leg\u00edtimo en todo el nodo. Debido a que la amplificaci\u00f3n ocurre dentro de una \u00fanica conexi\u00f3n, los l\u00edmites de conexi\u00f3n de la capa de red y la limitaci\u00f3n de velocidad no lo mitigan.\n\nLa soluci\u00f3n a\u00f1ade una opci\u00f3n :max_channels_per_transport (por defecto 100) que limita el n\u00famero de canales a los que puede unirse un \u00fanico proceso de transporte, obligando a los clientes abusivos a abrir muchas conexiones en su lugar, donde los balanceadores de carga externos y los proxies inversos pueden estrangularlos.\n\nEste problema afecta a phoenix: desde 0.11.0 antes de 1.5.15, desde 1.6.0-rc.0 antes de 1.6.17, desde 1.7.0-rc.0 antes de 1.7.24, y desde 1.8.0-rc.0 antes de 1.8.9."}], "id": "CVE-2026-56811", "lastModified": "2026-10-25T20:10:00.147", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.7, "baseSeverity": "HIGH", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-56811", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-07-07T16:12:27.662417Z", "version": "2.0.3"}}]}, "published": "2026-07-07T16:16:40.710", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Mitigation", "Patch", "Third Party Advisory"], "url": "https://cna.erlef.org/cves/CVE-2026-56811.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/phoenixframework/phoenix/commit/14a297e88023cb280a577962a49a0bbdeef9f4eb"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch"], "url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Patch", "Vendor Advisory"], "url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "tags": ["Mitigation", "Third Party Advisory"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-770"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0.11.0,1.5.15)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.6.0-rc.0,1.6.17)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.7.0-rc.0,1.7.24)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.8.0-rc.0,1.8.9)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "phoenix", "source": "cna", "vendor": "phoenixframework"}, "product": "phoenix", "vendor": "phoenixframework"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "14a297e88023cb280a577962a49a0bbdeef9f4eb"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "phoenix", "source": "cna", "vendor": "phoenixframework"}, "product": "phoenix", "vendor": "phoenixframework"}], "created": "2026-07-07T17:30:17.064370+00:00", "updated": "2026-08-01T17:30:07.738817+00:00", "vendors": ["phoenixframework", "phoenixframework$PRODUCT$phoenix"]}