CVE-2026-12803

UNKNOWN 0.0

KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery)

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-354
Vendor	legion of the bouncy castle inc.
Product	bc-java
Published	Aug 3, 2026

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Affected Versions

Legion of the Bouncy Castle Inc. / BC-JAVA

0 < 1.85

Legion of the Bouncy Castle Inc. / BC-LTS-JAVA

2.73.0 < 2.73.12

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/bcgit/bc-java/wiki/CVE-2026-12803 github.com: https://github.com/bcgit/bc-java/commit/697794413ebf7bc5e3fce609a707826ba52981af github.com: https://github.com/bcgit/bc-java/commit/7d79aa76e984da85f2a541cae8ba2ae56e1713bc

Credits

🔍 Alex Gaynor in collaboration with Claude and Anthropic Research