Vulnerability 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.
Related Weaknesses (CWE)
References
- https://github.com/bcgit/bc-csharp/commit/eaa42e1e8125b3e2e25e365c4194c7cd593236
- https://github.com/bcgit/bc-csharp/commit/f881400b761134160ec2a05fd27c3e56945378
- https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63567
FAQ
What is CVE-2026-63567?
CVE-2026-63567 is a documented vulnerability. 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 mod...
How severe is CVE-2026-63567?
CVSS scoring is not yet available for CVE-2026-63567. Check NVD for updates.
Is there a patch for CVE-2026-63567?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.