CVE-2026-63566

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63566", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "state": "PUBLISHED", "assignerShortName": "bcorg", "dateReserved": "2026-07-16T23:48:46.075Z", "datePublished": "2026-10-02T06:57:21.718Z", "dateUpdated": "2026-10-02T18:08:57.485Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-10-02T06:57:21.718Z"}, "title": "DTLS handshake reassembler allocates buffer from unchecked 24-bit length", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-789", "description": "CWE-789 Memory Allocation with Excessive Size Value", "type": "CWE"}]}], "impacts": [{"descriptions": [{"lang": "en", "value": "Denial of Service (memory exhaustion before handshake authentication)"}]}], "affected": [{"vendor": "Legion of the Bouncy Castle Inc.", "product": "bc-csharp", "collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography", "packageName": "BouncyCastle.Cryptography", "repo": "https://github.com/bcgit/bc-csharp", "programFiles": ["crypto/src/tls/DtlsReliableHandshake.cs", "crypto/src/tls/DtlsReassembler.cs"], "versions": [{"status": "affected", "version": "0", "lessThan": "2.7.0", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not."}]}], "references": [{"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3", "tags": ["patch"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "HIGH", "baseScore": 8.7, "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"}}], "credits": [{"lang": "en", "value": "Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.", "type": "finder"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "Claude Opus 5.5"}, "x_antReportIds": ["ANT-2026-67TQHZ95", "ANT-2026-EWREHKZ5"]}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-10-02T18:07:25.493590Z", "id": "CVE-2026-63566", "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": "2026-10-02T18:08:57.485Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-63566", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-02T18:07:25.493590Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-02T18:08:43.262Z"}}], "cna": {"title": "DTLS handshake reassembler allocates buffer from unchecked 24-bit length", "source": {"discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research."}], "impacts": [{"descriptions": [{"lang": "en", "value": "Denial of Service (memory exhaustion before handshake authentication)"}]}], "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", "exploitMaturity": "NOT_DEFINED", "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": [{"repo": "https://github.com/bcgit/bc-csharp", "vendor": "Legion of the Bouncy Castle Inc.", "product": "bc-csharp", "versions": [{"status": "affected", "version": "0", "lessThan": "2.7.0", "versionType": "semver"}], "packageName": "BouncyCastle.Cryptography", "programFiles": ["crypto/src/tls/DtlsReliableHandshake.cs", "crypto/src/tls/DtlsReassembler.cs"], "collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography", "defaultStatus": "unaffected"}], "references": [{"url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3", "tags": ["patch"]}, {"url": "https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda", "tags": ["patch"]}], "x_generator": {"engine": "Claude Opus 5.5"}, "descriptions": [{"lang": "en", "value": "Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.", "supportingMedia": [{"type": "text/html", "value": "Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-789", "description": "CWE-789 Memory Allocation with Excessive Size Value"}]}], "x_antReportIds": ["ANT-2026-67TQHZ95", "ANT-2026-EWREHKZ5"], "providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-10-02T06:57:21.718Z"}}}, "cveMetadata": {"cveId": "CVE-2026-63566", "state": "PUBLISHED", "dateUpdated": "2026-10-02T18:08:57.485Z", "dateReserved": "2026-07-16T23:48:46.075Z", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "datePublished": "2026-10-02T06:57:21.718Z", "assignerShortName": "bcorg"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography", "defaultStatus": "unaffected", "packageName": "BouncyCastle.Cryptography", "product": "bc-csharp", "programFiles": ["crypto/src/tls/DtlsReliableHandshake.cs", "crypto/src/tls/DtlsReassembler.cs"], "repo": "https://github.com/bcgit/bc-csharp", "vendor": "Legion of the Bouncy Castle Inc.", "versions": [{"lessThan": "2.7.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*", "matchCriteriaId": "21A715E8-41BE-47EB-833D-07B9908CCF31", "versionEndExcluding": "2.7.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not."}], "id": "CVE-2026-63566", "lastModified": "2026-10-27T16:25:06.960", "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": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-63566", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-10-02T18:07:25.493590Z", "version": "2.0.3"}}]}, "published": "2026-10-02T07:16:36.973", "references": [{"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "tags": ["Patch"], "url": "https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3"}, {"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "tags": ["Patch"], "url": "https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda"}, {"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "tags": ["Patch", "Vendor Advisory"], "url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63566"}], "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-789"}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2.7.0)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "cna", "scores": [{"score": 100.0, "source": "cna"}]}, "product": "bc-csharp", "vendor": "legion_of_the_bouncy_castle_inc."}], "created": "2026-10-02T09:15:08.529528+00:00", "updated": "2026-10-04T20:55:54.055460+00:00", "vendors": ["legion_of_the_bouncy_castle_inc.", "legion_of_the_bouncy_castle_inc.$PRODUCT$bc-csharp"]}