{"id":"CVE-2026-63567","revision":null,"records":[{"revision":"c781a27c98494d509186a6076dfea497","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63567","aliases":[],"title":"IesEngine block-cipher mode checks padding before MAC (CBC padding oracle)","description":"Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under the same key pair, to recover its plaintext via a CBC padding-oracle attack, because in block-cipher mode the engine decrypts the ciphertext and removes its padding before verifying the MAC. A padding failure is therefore reported with a different error message, and without the MAC computation, compared with a MAC failure. Only applications that construct IesEngine directly with a padded block cipher, such as AES in CBC mode with PKCS#7 padding, are affected; stream-mode IES is not.","state":0,"publishedAt":"2026-10-02T06:58:32.487+00:00","modifiedAt":"2026-10-02T18:09:54.933+00:00","affected":[{"ecosystem":"https://www.nuget.org/packages/BouncyCastle.Cryptography","name":"BouncyCastle.Cryptography","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Legion of the Bouncy Castle Inc.\",\n                    \"product\": \"bc-csharp\",\n                    \"collectionURL\": \"https://www.nuget.org/packages/BouncyCastle.Cryptography\",\n                    \"packageName\": \"BouncyCastle.Cryptography\",\n                    \"repo\": \"https://github.com/bcgit/bc-csharp\",\n                    \"programFiles\": [\n                        \"crypto/src/crypto/engines/IesEngine.cs\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"0\",\n                            \"lessThan\": \"2.7.0\",\n                            \"versionType\": \"semver\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","score":8.2,"severity":"HIGH"}],"references":["https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63567","https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d","https://github.com/bcgit/bc-csharp/commit/eaa42e1e8125b3e2e25e365c4194c7cd5932360b"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63567","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63567","identifiers":["CVE-2026-63567"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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