CVE-2026-16000: legion of the bouncy castle inc. bc-csharp Missing Cryptographic Step

Vulnerability summary

CVE-2026-16000 is a high (CVSS 8.7) Missing Cryptographic Step vulnerability in legion of the bouncy castle inc. bc-csharp. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.8% of scored vulnerabilities.

Timeline

1. 02-10-2026
   PublishedVulnerability first disclosed.
2. 02-10-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-325Missing Cryptographic StepThe product does not implement a required step in a cryptographic algorithm, resulting in weaker encryption than advertised by the algorithm.