{"schema":"threatline.record/2","record":{"id":"CVE-2026-15999","aliases":[],"summary":"AES-CCM decryption accepts zero or out-of-range tag length, bypassing authentication","details":"Improper validation of integrity check value in the AES-CCM implementation (CcmParameters and CcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to modify CCM-encrypted content without detection via an AlgorithmIdentifier whose CCMParameters declare an authentication tag (aes-ICVlen) of zero or another length outside the RFC 5084 set, because CcmParameters accepted any value and CcmBlockCipher validated the tag length only when encrypting, so decryption compared a zero-length or very short tag. Affected paths include ParameterUtilities.GetCipherParameters, used by CmsEnvelopedData and CmsEnvelopedDataParser for EnvelopedData encrypted with AES-CCM, and any caller passing an unchecked tag length to CcmBlockCipher for decryption.","categories":["Unclassified"],"product":"bc-csharp","vendor":"Legion of the Bouncy Castle Inc.","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-15999","source_modified_at":"2026-10-02T18:02:14.715Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"bc-csharp","vendor":"Legion of the Bouncy Castle Inc.","versions":[{"status":"affected","version":"0","lessThan":"2.7.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-15999","source_modified_at":"2026-10-02T18:02:14.715Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"bc-csharp","ecosystem":null},"version":"2.7.0","basis":"first unaffected version stated in the CVE record"}],"cvss":8.2,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00227,"percentile":0.12725,"score_date":"2026-10-23"},"published_at":"2026-10-02T06:52:16.792Z","modified_at":"2026-10-02T18:02:14.715Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-15999","fetched_at":"2026-10-23T18:52:38.922436Z","source_modified_at":"2026-10-02T18:02:14.715Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-15999","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-csharp/wiki/CVE-2026-15999","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-csharp/commit/2818bdfa55efd58b0d6a1c75f360b8404d879780","tags":["patch"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-csharp/commit/9d284d8f379614def853b590c62bbb31c48f7af0","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":"2026-10-02T18:01:58.140745Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-02T18:02:14.715Z","content_hash":"c917296e76585e9b580a0ee876c473dd5895f8e375d750689aeaafcf82bc7d03"}}