CVE-2026-12803

Weakness

In Bouncy Castle for Java before 1.85, KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery). This issue also affects Bouncy Castle for Java LTS before 2.73.12.

Affected products

• bouncycastle bc-java
• bouncycastle bouncy_castle_for_java_lts

References

• https://github.com/bcgit/bc-java/commit/697794413ebf7bc5e3fce609a707826ba52981af
• https://github.com/bcgit/bc-java/commit/7d79aa76e984da85f2a541cae8ba2ae56e1713bc
• https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9012803