CVE-2026-12803: KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery)
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 Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-12803?
CVE-2026-12803 has a high severity rating of 8.7 according to the CVSS score.
How do I fix CVE-2026-12803?
To mitigate CVE-2026-12803, upgrade Bouncy Castle for Java to version 1.85 or later, or Bouncy Castle for Java LTS to version 2.73.12 or later.
What is the impact of CVE-2026-12803?
CVE-2026-12803 allows for potential cross-nonce AEAD forgery when the Additional Authenticated Data (AAD) is absent.
Which versions of Bouncy Castle are affected by CVE-2026-12803?
CVE-2026-12803 affects Bouncy Castle for Java versions prior to 1.85 and Bouncy Castle for Java LTS versions before 2.73.12.
Is CVE-2026-12803 exploitable in my application?
If your application uses affected versions of Bouncy Castle without proper nonce binding when AAD is absent, it may be vulnerable to CVE-2026-12803.