{"schema":"threatline.record/2","record":{"id":"CVE-2026-71886","aliases":[],"summary":"OpenPGP certification accepted from a subkey without certification authority","details":"In Bouncy Castle for Java before 1.86, the high-level OpenPGP certificate API accepted a third-party certification or trust delegation from any component key of the issuing certificate, without requiring that component to have been granted the authority to certify. OpenPGPCertificate.getCertificationBy() and getDelegationBy() resolve a third-party signature by matching its issuer key identifier against every key of the third-party certificate, then verify the issuing component's binding chain and the signature itself; nothing checked that the issuing component carried the RFC 9580 sec. 5.2.3.29 certification key flag (CERTIFY_OTHER) when the signature was created. A subkey bound only with SIGN_DATA - the online signing subkey of exactly the offline-primary arrangement those key flags exist to express - could therefore issue a positive User ID certification over an attacker-controlled identity, or a full-trust depth-one direct-key delegation of introducer trust, and the API returned it as a valid signature chain attributed to the third-party certificate. An application treating getCertificationBy(...).isValid() or getDelegationBy(...) as an identity or trusted-introducer decision would attribute the attacker's assertion to the offline primary key. The same held for a legacy RSA subkey bound only for encryption, whose algorithm is nonetheless able to sign. This does not forge the primary key's signature or recover any private key; it promotes an already-compromised restricted subkey to the primary key's identity-issuing authority, defeating the containment the key-flag separation provides. A third-party certification or delegation is now attributed to the issuing certificate only when the component key that made it is the primary key, or is a subkey holding CERTIFY_OTHER when the signature was created, so certification-capable subkeys continue to be accepted; primary keys are accepted whatever their key flags say, since a primary key is certification-capable by construction and certificates carrying no key flags subpacket at all are common. Third-party revocations are deliberately outside the rule, since declining to honour one would keep trust alive rather than withdraw it.","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-2026-71886","source_modified_at":"2026-10-05T16:03:23.403Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"BC-JAVA","vendor":"Legion of the Bouncy Castle Inc.","versions":[{"status":"affected","version":"1.81","lessThan":"1.86","versionType":"maven"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-71886","source_modified_at":"2026-10-05T16:03:23.403Z","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"}],"cvss":8.2,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00167,"percentile":0.05615,"score_date":"2026-10-23"},"published_at":"2026-10-03T08:46:33.868Z","modified_at":"2026-10-05T16:03:23.403Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-71886","fetched_at":"2026-10-23T18:52:38.922436Z","source_modified_at":"2026-10-05T16:03:23.403Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-71886","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%9071886","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-java/commit/f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb","tags":["patch"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-05T16:02:59.243532Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-05T16:03:23.403Z","content_hash":"9ca1ddbbd3954278c64b5abb238347709a3f6f9e2e7868af9ea79d8a6bb78522"}}