CVE-2026-16000 (GCVE-0-2026-16000)

Vulnerability from cvelistv5 – Published: 2026-10-02 06:54 – Updated: 2026-10-02 18:00
VLAI
Title
KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used
Summary
Missing cryptographic step in the DSTU 7624 CCM mode implementation (KCcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can observe encrypted messages of known or chosen content to forge ciphertexts with valid authentication tags, via messages encrypted without associated data. The cause is that the G1 block, which binds the nonce, the message length and the parameter flags into the CBC-MAC, was processed only when associated data was present. Without associated data the tag was a CBC-MAC of the plaintext alone, independent of the nonce. Only applications that use KCcmBlockCipher directly and supply no associated data are affected.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-02 17:57 UTC
CWE
  • CWE-325 - Missing Cryptographic Step
Assigner
References
Impacted products
Vendor Product Version CPE status
Legion of the Bouncy Castle Inc. bc-csharp Affected: 0 , < 2.7.0 (semver)
guessed Create a notification for this product.
Credits
Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.
Show details on NVD website
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