{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.7.0"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4007498b13582d90ee1eda5d9920c324428b98b3"
            },
            {
              "fixed": "eaa42e1e8125b3e2e25e365c4194c7cd5932360b"
            },
            {
              "fixed": "f881400b761134160ec2a05fd27c3e569453788d"
            }
          ],
          "repo": "https://github.com/bcgit/bc-csharp",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "bcorg",
    "cwe_ids": [
      "CWE-203"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63567.json"
  },
  "details": "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.",
  "id": "CVE-2026-63567",
  "modified": "2026-10-04T02:30:52.032846594Z",
  "published": "2026-10-02T06:58:32.487Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://www.nuget.org/packages/BouncyCastle.Cryptography"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63567.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63567"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63567"
    },
    {
      "type": "FIX",
      "url": "https://github.com/bcgit/bc-csharp/commit/eaa42e1e8125b3e2e25e365c4194c7cd5932360b"
    },
    {
      "type": "FIX",
      "url": "https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e569453788d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bcgit/bc-csharp"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "IesEngine block-cipher mode checks padding before MAC (CBC padding oracle)"
}