CVE-2026-86688

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-86688", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-09-17T00:30:01.485Z", "datePublished": "2026-09-17T21:58:00.853Z", "dateUpdated": "2026-09-18T14:31:41.961Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "ash_authentication", "packageURL": "pkg:hex/ash_authentication", "product": "ash_authentication", "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "versions": [{"lessThan": "4.15.0", "status": "affected", "version": "0.2.0", "versionType": "semver"}, {"lessThan": "5.0.0-rc.14", "status": "affected", "version": "5.0.0-rc.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "team-alembic/ash_authentication", "packageURL": "pkg:github/team-alembic/ash_authentication", "product": "ash_authentication", "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "versions": [{"changes": [{"at": "872db454405ecad4fcdabd9ff3d8755d1d6a69ae", "status": "unaffected"}, {"at": "3e1d452cbf1564e87f5f97be882b66fe25af7cfa", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "a939dde9b917c072cdf10c4b0913a9886a4b0231", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.</p>\n<p>Phoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a <code>return_to</code> value, still survive into the authenticated session there.</p>"}, {"base64": false, "type": "text/markdown", "value": "Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.\n\nPhoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a `return_to` value, still survive into the authenticated session there."}], "value": "Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.\n\nPhoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a return_to value, still survive into the authenticated session there."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*", "versionEndExcluding": "4.15.0", "versionStartIncluding": "0.2.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*", "versionEndExcluding": "5.0.0-rc.14", "versionStartIncluding": "5.0.0-rc.0", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "reporter", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "James Harton"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "dateAssigned": "2026-09-17T05:24:11.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.</p>\n<p><code>AshAuthentication.Plug.Helpers.store_in_session/2</code> writes the authenticated subject into the existing session with <code>Plug.Conn.put_session/3</code> and never calls <code>Plug.Conn.configure_session(renew: true)</code>, so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default <code>success/4</code> injected by <code>AshAuthentication.Phoenix.Controller.__using__/1</code>, the <code>AuthController</code> emitted by <code>mix ash_authentication_phoenix.install</code>, and remember-me auto-login. <code>AshAuthentication.Phoenix.Plug.store_in_session/2</code> is a <code>defdelegate</code> to it. Logout does not close the window either, because <code>clear_session/2</code> ends with <code>Plug.Conn.clear_session/1</code>, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.</p>\n<p>This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.</p>"}, {"base64": false, "type": "text/markdown", "value": "Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\n`AshAuthentication.Plug.Helpers.store_in_session/2` writes the authenticated subject into the existing session with `Plug.Conn.put_session/3` and never calls `Plug.Conn.configure_session(renew: true)`, so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default `success/4` injected by `AshAuthentication.Phoenix.Controller.__using__/1`, the `AuthController` emitted by `mix ash_authentication_phoenix.install`, and remember-me auto-login. `AshAuthentication.Phoenix.Plug.store_in_session/2` is a `defdelegate` to it. Logout does not close the window either, because `clear_session/2` ends with `Plug.Conn.clear_session/1`, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."}], "value": "Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\nAshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."}], "impacts": [{"capecId": "CAPEC-61", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store.</p>"}, {"base64": false, "type": "text/markdown", "value": "An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store."}], "value": "An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store."}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 7.4, "baseSeverity": "HIGH", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-384", "description": "CWE-384 Session Fixation", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-17T21:58:00.853Z"}, "references": [{"name": "GitHub Advisory", "tags": ["related", "vendor-advisory"], "url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-v577-944g-7h3x"}, {"name": "EEF CNA record for CVE-2026-86688", "tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-86688.html"}, {"name": "OSV record EEF-CVE-2026-86688", "tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-86688"}, {"name": "Introducing commit a939dde in team-alembic/ash_authentication", "tags": ["related"], "url": "https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231"}, {"name": "Fix commit 872db45 in team-alembic/ash_authentication", "tags": ["patch"], "url": "https://github.com/team-alembic/ash_authentication/commit/872db454405ecad4fcdabd9ff3d8755d1d6a69ae"}, {"name": "Fix commit 3e1d452 in team-alembic/ash_authentication", "tags": ["patch"], "url": "https://github.com/team-alembic/ash_authentication/commit/3e1d452cbf1564e87f5f97be882b66fe25af7cfa"}], "source": {"discovery": "EXTERNAL"}, "title": "Session id is not renewed on authentication in ash_authentication, allowing session fixation", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Call <code>Plug.Conn.configure_session(conn, renew: true)</code> in your own <code>success/4</code> before <code>store_in_session/2</code>. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.</p>\n<p>Add <code>Plug.Conn.configure_session(conn, drop: true)</code> at sign-out so a planted identifier does not survive a logout-then-login cycle.</p>"}, {"base64": false, "type": "text/markdown", "value": "Call `Plug.Conn.configure_session(conn, renew: true)` in your own `success/4` before `store_in_session/2`. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.\n\nAdd `Plug.Conn.configure_session(conn, drop: true)` at sign-out so a planted identifier does not survive a logout-then-login cycle."}], "value": "Call Plug.Conn.configure_session(conn, renew: true) in your own success/4 before store_in_session/2. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.\n\nAdd Plug.Conn.configure_session(conn, drop: true) at sign-out so a planted identifier does not survive a logout-then-login cycle."}]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-86688", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-09-18T14:24:09.606894Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-18T14:31:41.961Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-86688", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-09-18T14:24:09.606894Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-18T14:29:32.046Z"}}], "cna": {"title": "Session id is not renewed on authentication in ash_authentication, allowing session fixation", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "reporter", "value": "Peter Ullrich"}, {"lang": "en", "type": "remediation developer", "value": "James Harton"}, {"lang": "en", "type": "coordinator", "value": "Jonatan M\u00e4nnchen / EEF"}], "impacts": [{"capecId": "CAPEC-61", "descriptions": [{"lang": "en", "value": "An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store.", "supportingMedia": [{"type": "text/html", "value": "<p>An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store.</p>", "base64": false}, {"type": "text/markdown", "value": "An attacker holding a session identifier they planted before the victim signed in gains that victim's authenticated session, and with it full account takeover, in deployments using a server-side session store.", "base64": false}]}]}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 7.4, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "HIGH", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N", "providerUrgency": "NOT_DEFINED", "userInteraction": "ACTIVE", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "product": "ash_authentication", "versions": [{"status": "affected", "version": "0.2.0", "lessThan": "4.15.0", "versionType": "semver"}, {"status": "affected", "version": "5.0.0-rc.0", "lessThan": "5.0.0-rc.14", "versionType": "semver"}], "packageURL": "pkg:hex/ash_authentication", "packageName": "ash_authentication", "collectionURL": "https://repo.hex.pm", "defaultStatus": "unaffected"}, {"cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "product": "ash_authentication", "versions": [{"status": "affected", "changes": [{"at": "872db454405ecad4fcdabd9ff3d8755d1d6a69ae", "status": "unaffected"}, {"at": "3e1d452cbf1564e87f5f97be882b66fe25af7cfa", "status": "unaffected"}], "version": "a939dde9b917c072cdf10c4b0913a9886a4b0231", "lessThan": "*", "versionType": "git"}], "packageURL": "pkg:github/team-alembic/ash_authentication", "packageName": "team-alembic/ash_authentication", "collectionURL": "https://github.com", "defaultStatus": "unaffected"}], "references": [{"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-v577-944g-7h3x", "name": "GitHub Advisory", "tags": ["related", "vendor-advisory"]}, {"url": "https://cna.erlef.org/cves/CVE-2026-86688.html", "name": "EEF CNA record for CVE-2026-86688", "tags": ["related"]}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-86688", "name": "OSV record EEF-CVE-2026-86688", "tags": ["related"]}, {"url": "https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231", "name": "Introducing commit a939dde in team-alembic/ash_authentication", "tags": ["related"]}, {"url": "https://github.com/team-alembic/ash_authentication/commit/872db454405ecad4fcdabd9ff3d8755d1d6a69ae", "name": "Fix commit 872db45 in team-alembic/ash_authentication", "tags": ["patch"]}, {"url": "https://github.com/team-alembic/ash_authentication/commit/3e1d452cbf1564e87f5f97be882b66fe25af7cfa", "name": "Fix commit 3e1d452 in team-alembic/ash_authentication", "tags": ["patch"]}], "workarounds": [{"lang": "en", "value": "Call Plug.Conn.configure_session(conn, renew: true) in your own success/4 before store_in_session/2. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.\n\nAdd Plug.Conn.configure_session(conn, drop: true) at sign-out so a planted identifier does not survive a logout-then-login cycle.", "supportingMedia": [{"type": "text/html", "value": "<p>Call <code>Plug.Conn.configure_session(conn, renew: true)</code> in your own <code>success/4</code> before <code>store_in_session/2</code>. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.</p>\n<p>Add <code>Plug.Conn.configure_session(conn, drop: true)</code> at sign-out so a planted identifier does not survive a logout-then-login cycle.</p>", "base64": false}, {"type": "text/markdown", "value": "Call `Plug.Conn.configure_session(conn, renew: true)` in your own `success/4` before `store_in_session/2`. This is a one-line change in application code and closes the controller sign-in path, though not remember-me auto-login, which does not pass through application code.\n\nAdd `Plug.Conn.configure_session(conn, drop: true)` at sign-out so a planted identifier does not survive a logout-then-login cycle.", "base64": false}]}], "dateAssigned": "2026-09-17T05:24:11.000Z", "descriptions": [{"lang": "en", "value": "Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\nAshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.", "supportingMedia": [{"type": "text/html", "value": "<p>Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.</p>\n<p><code>AshAuthentication.Plug.Helpers.store_in_session/2</code> writes the authenticated subject into the existing session with <code>Plug.Conn.put_session/3</code> and never calls <code>Plug.Conn.configure_session(renew: true)</code>, so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default <code>success/4</code> injected by <code>AshAuthentication.Phoenix.Controller.__using__/1</code>, the <code>AuthController</code> emitted by <code>mix ash_authentication_phoenix.install</code>, and remember-me auto-login. <code>AshAuthentication.Phoenix.Plug.store_in_session/2</code> is a <code>defdelegate</code> to it. Logout does not close the window either, because <code>clear_session/2</code> ends with <code>Plug.Conn.clear_session/1</code>, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.</p>\n<p>This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.</p>", "base64": false}, {"type": "text/markdown", "value": "Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\n`AshAuthentication.Plug.Helpers.store_in_session/2` writes the authenticated subject into the existing session with `Plug.Conn.put_session/3` and never calls `Plug.Conn.configure_session(renew: true)`, so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default `success/4` injected by `AshAuthentication.Phoenix.Controller.__using__/1`, the `AuthController` emitted by `mix ash_authentication_phoenix.install`, and remember-me auto-login. `AshAuthentication.Phoenix.Plug.store_in_session/2` is a `defdelegate` to it. Logout does not close the window either, because `clear_session/2` ends with `Plug.Conn.clear_session/1`, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-384", "description": "CWE-384 Session Fixation"}]}], "configurations": [{"lang": "en", "value": "Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.\n\nPhoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a return_to value, still survive into the authenticated session there.", "supportingMedia": [{"type": "text/html", "value": "<p>Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.</p>\n<p>Phoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a <code>return_to</code> value, still survive into the authenticated session there.</p>", "base64": false}, {"type": "text/markdown", "value": "Exploitation for account takeover requires a server-side session store (ETS, Mnesia, Redis or a database), where the cookie carries a stable session identifier, and a position from which the attacker can plant that cookie in the victim's browser: cookie tossing from a sibling subdomain, an HTTP host without HSTS, or a shared or kiosk browser.\n\nPhoenix defaults to the signed cookie store, and neither package's installer changes it. Under that store the authenticated session lives in the re-signed cookie delivered only to the victim, so a planted pre-authentication copy does not become an authenticated session. Attacker-planted session contents, such as a `return_to` value, still survive into the authenticated session there.", "base64": false}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "4.15.0", "versionStartIncluding": "0.2.0"}, {"criteria": "cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.0.0-rc.14", "versionStartIncluding": "5.0.0-rc.0"}], "operator": "OR"}], "operator": "AND"}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-17T21:58:00.853Z"}}}, "cveMetadata": {"cveId": "CVE-2026-86688", "state": "PUBLISHED", "dateUpdated": "2026-09-18T14:31:41.961Z", "dateReserved": "2026-09-17T00:30:01.485Z", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "datePublished": "2026-09-17T21:58:00.853Z", "assignerShortName": "EEF"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "ash_authentication", "packageURL": "pkg:hex/ash_authentication", "product": "ash_authentication", "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "versions": [{"lessThan": "4.15.0", "status": "affected", "version": "0.2.0", "versionType": "semver"}, {"lessThan": "5.0.0-rc.14", "status": "affected", "version": "5.0.0-rc.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "packageName": "team-alembic/ash_authentication", "packageURL": "pkg:github/team-alembic/ash_authentication", "product": "ash_authentication", "repo": "https://github.com/team-alembic/ash_authentication", "vendor": "team-alembic", "versions": [{"changes": [{"at": "872db454405ecad4fcdabd9ff3d8755d1d6a69ae", "status": "unaffected"}, {"at": "3e1d452cbf1564e87f5f97be882b66fe25af7cfa", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "a939dde9b917c072cdf10c4b0913a9886a4b0231", "versionType": "git"}]}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\nAshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."}], "id": "CVE-2026-86688", "lastModified": "2026-09-18T18:16:18.527", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 7.4, "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": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/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": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-86688", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-09-18T14:24:09.606894Z", "version": "2.0.3"}}]}, "published": "2026-09-17T22:17:04.180", "references": [{"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://cna.erlef.org/cves/CVE-2026-86688.html"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/team-alembic/ash_authentication/commit/3e1d452cbf1564e87f5f97be882b66fe25af7cfa"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/team-alembic/ash_authentication/commit/872db454405ecad4fcdabd9ff3d8755d1d6a69ae"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-v577-944g-7h3x"}, {"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "url": "https://osv.dev/vulnerability/EEF-CVE-2026-86688"}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-384"}], "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0.2.0,4.15.0)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[5.0.0-rc.0,5.0.0-rc.14)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "inferred", "scores": [{"score": 100.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "ash_authentication", "source": "cna", "vendor": "team-alembic"}, "product": "ash_authentication", "vendor": "team-alembic"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[a939dde9b917c072cdf10c4b0913a9886a4b0231,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "inferred", "scores": [{"score": 100.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "ash_authentication", "source": "cna", "vendor": "team-alembic"}, "product": "ash_authentication", "vendor": "team-alembic"}], "created": "2026-09-18T13:00:10.730961+00:00", "updated": "2026-09-18T23:45:15.931367+00:00", "vendors": ["team-alembic", "team-alembic$PRODUCT$ash_authentication"]}