{"schema":"threatline.record/2","record":{"id":"CVE-2026-71892","aliases":[],"summary":"CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys","details":"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).","categories":["Unclassified"],"product":"BC-JAVA","vendor":"Legion of the Bouncy Castle Inc.","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","source_modified_at":"2026-10-05T16:58:40.411Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"BC-JAVA","vendor":"Legion of the Bouncy Castle Inc.","versions":[{"status":"affected","version":"1.78","lessThan":"1.86","versionType":"maven"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","source_modified_at":"2026-10-05T16:58:40.411Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"BC-FJA","vendor":"Legion of the Bouncy Castle Inc.","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"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","source_modified_at":"2026-10-05T16:58:40.411Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"BC-JAVA","ecosystem":null},"version":"1.86","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","source_modified_at":"2026-10-05T16:58:40.411Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"BC-FJA","ecosystem":null},"version":"2.0.13","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","source_modified_at":"2026-10-05T16:58:40.411Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"BC-FJA","ecosystem":null},"version":"2.1.13","basis":"first unaffected version stated in the CVE record"}],"cvss":6.9,"severity":"Medium","kev":{"listed":false},"epss":{"probability":0.00173,"percentile":0.06414,"score_date":"2026-10-23"},"published_at":"2026-10-03T08:30:26.982Z","modified_at":"2026-10-05T16:58:40.411Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-71892","fetched_at":"2026-10-23T18:52:38.922436Z","source_modified_at":"2026-10-05T16:58:40.411Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-71892","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071892","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-java/commit/be0a7d925c818ef2f338bcec55178b9b6336dfc3","tags":["patch"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"yes","technical_impact":"partial","assessed_at":"2026-10-05T16:58:15.636238Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-05T16:58:40.411Z","content_hash":"fd7ac1459c781b6019ddda7d7e62d7aa80a2b76ebe863dfdf255c586a1544c08"}}