CVE-2026-12803: Bouncycastle Bc-Java

High severity, CVSS 7.5. EPSS: 0.2% chance of exploitation in the next 30 days.

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: before 1.85 (fixed in 1.85)
• Bouncycastle Bouncy Castle For Java LTS: up to and including 2.73.11

Published 2026-08-03. Last modified 2026-09-02.