CVE-2026-16000
Received Received - Intake

DSTU 7624 CCM Mode Cryptographic Weakness in Bouncy Castle

Publication date: 2026-10-02

Last updated on: 2026-10-02

Assigner: bcorg

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.

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Meta Information

Published
2026-10-02
Last Modified
2026-10-02
Generated
2026-10-02
AI Q&A
2026-10-02
EPSS Evaluated
N/A
NVD
CVE-2026-16000
EUVD
EUVD-2026-91205

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
bouncy_castle bc_csharp 2.6.2
bouncy_castle bc_csharp 2.7.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-325 The product does not implement a required step in a cryptographic algorithm, resulting in weaker encryption than advertised by the algorithm.

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Executive Summary

This vulnerability is in the Bouncy Castle Cryptography library's implementation of the KCcmBlockCipher for the DSTU 7624 encryption mode. The issue occurs when messages are encrypted without associated data. The authentication tag then depends only on the plaintext, not the nonce or message length, allowing attackers to forge valid tags by observing ciphertexts and knowing or choosing plaintext.

Detection Guidance

To detect this vulnerability, check if your system uses Bouncy Castle Cryptography library's KCcmBlockCipher in DSTU 7624 CCM mode without associated data. Inspect the library version; versions 2.6.2 and earlier are vulnerable. Use commands like 'dotnet list package' or check project dependencies for bc-csharp versions below 2.7.0.

Impact Analysis

If you use applications that directly employ the KCcmBlockCipher without associated data, an attacker could forge ciphertexts with valid authentication tags. This breaks the integrity protection of encrypted messages, potentially allowing unauthorized data tampering or decryption without detection.

Compliance Impact

This vulnerability could compromise data integrity and confidentiality, which are core requirements under GDPR and HIPAA. Forged ciphertexts may lead to unauthorized data access or tampering, potentially violating compliance with these regulations.

Mitigation Strategies

Immediately upgrade to Bouncy Castle C# .NET version 2.7.0 or later. If upgrading is not possible, ensure all KCcmBlockCipher operations include non-empty associated data that is a multiple of the cipher block size. Avoid using KCcmBlockCipher without associated data in vulnerable versions.

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