---
id: CVE-2026-16000
title: >-
  Missing cryptographic step in the DSTU 7624 CCM mode implementation
  (KCcmBlockCipher) in Legion of the Bouncy Castle Inc
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 ci…
severity: high
cvss: 8.7
cvssVector: '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'
cwe:
  - CWE-325
vendor: Legion of the Bouncy Castle Inc.
product: BouncyCastle.Cryptography
affected:
  - BouncyCastle.Cryptography < 2.7.0
published: '2026-10-02'
updated: '2026-10-02'
sourceUpdated: '2026-10-02T07:16:36.400'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-16000'
references:
  - url: >-
      https://github.com/bcgit/bc-csharp/commit/b01e9e6c0e231b90867fbaf03bf148bde6f9ccfb
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: 'https://github.com/bcgit/bc-csharp/wiki/CVE-2026-16000'
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-10-02T07:13:06.672Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.