{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-71892", "assignerOrgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "state": "PUBLISHED", "assignerShortName": "bcorg", "dateReserved": "2026-08-08T00:06:07.401Z", "datePublished": "2026-10-03T08:30:26.982Z", "dateUpdated": "2026-10-03T08:30:26.982Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "91579145-5d7b-4cc5-b925-a0262ff19630", "shortName": "bcorg", "dateUpdated": "2026-10-03T08:30:26.982Z"}, "title": "CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-697", "description": "CWE-697 Incorrect Comparison", "type": "CWE"}]}], "affected": [{"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-JAVA", "platforms": ["all"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/", "packageName": "bcpkix", "repo": "https://github.com/bcgit/bc-java", "packageURL": "pkg:maven/org.bouncycastle/bcpkix-jdk18on", "modules": ["pkix"], "programFiles": ["JceKeyTransRecipient"], "versions": [{"status": "affected", "version": "1.78", "lessThan": "1.86", "versionType": "maven"}], "defaultStatus": "unaffected"}, {"vendor": "Legion of the Bouncy Castle Inc.", "product": "BC-FJA", "platforms": ["all"], "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/", "packageName": "bcpkix-fips", "packageURL": "pkg:maven/org.bouncycastle/bcpkix-fips", "versions": [{"status": "affected", "version": "2.0.7", "lessThan": "2.0.13", "versionType": "maven"}, {"status": "affected", "version": "2.1.0", "lessThan": "2.1.13", "versionType": "maven"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<p>In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).</p>"}]}], "references": [{"url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071892", "tags": ["vendor-advisory"]}, {"url": "https://github.com/bcgit/bc-java/commit/be0a7d925c818ef2f338bcec55178b9b6336dfc3", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "LOW", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "AMBER", "version": "4.0", "baseSeverity": "MEDIUM", "baseScore": 6.9, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/U:Amber"}}], "credits": [{"lang": "en", "value": "Yu Bao from the PayPal Cyber Security Team", "type": "reporter"}], "source": {"discovery": "EXTERNAL"}, "x_generator": {"engine": "bc release-notes template"}}}}

{}

{"affected": [{"affectedData": [{"collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/", "defaultStatus": "unaffected", "modules": ["pkix"], "packageName": "bcpkix", "packageURL": "pkg:maven/org.bouncycastle/bcpkix-jdk18on", "platforms": ["all"], "product": "BC-JAVA", "programFiles": ["JceKeyTransRecipient"], "repo": "https://github.com/bcgit/bc-java", "vendor": "Legion of the Bouncy Castle Inc.", "versions": [{"lessThan": "1.86", "status": "affected", "version": "1.78", "versionType": "maven"}]}, {"collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/", "defaultStatus": "unaffected", "packageName": "bcpkix-fips", "packageURL": "pkg:maven/org.bouncycastle/bcpkix-fips", "platforms": ["all"], "product": "BC-FJA", "vendor": "Legion of the Bouncy Castle Inc.", "versions": [{"lessThan": "2.0.13", "status": "affected", "version": "2.0.7", "versionType": "maven"}, {"lessThan": "2.1.13", "status": "affected", "version": "2.1.0", "versionType": "maven"}]}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series)."}], "id": "CVE-2026-71892", "lastModified": "2026-10-03T09:17:05.913", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.9, "baseSeverity": "MEDIUM", "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": "AMBER", "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:L/VI:L/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:Amber", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}]}, "published": "2026-10-03T09:17:05.913", "references": [{"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "url": "https://github.com/bcgit/bc-java/commit/be0a7d925c818ef2f338bcec55178b9b6336dfc3"}, {"source": "91579145-5d7b-4cc5-b925-a0262ff19630", "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071892"}], "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-697"}], "source": "91579145-5d7b-4cc5-b925-a0262ff19630", "type": "Secondary"}]}

{}

{}