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.
History

Tue, 27 Oct 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Bouncycastle
Bouncycastle bc-csharp
CPEs cpe:2.3:a:bouncycastle:bc-csharp:*:*:*:*:*:*:*:*
Vendors & Products Bouncycastle
Bouncycastle bc-csharp
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}


Sun, 04 Oct 2026 06:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 02 Oct 2026 15:15:00 +0000

Type Values Removed Values Added
First Time appeared Legion Of The Bouncy Castle Inc.
Legion Of The Bouncy Castle Inc. bc-csharp
Vendors & Products Legion Of The Bouncy Castle Inc.
Legion Of The Bouncy Castle Inc. bc-csharp

Fri, 02 Oct 2026 07:15:00 +0000

Type Values Removed Values Added
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.
Title KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used
Weaknesses CWE-325
References
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: bcorg

Published: 2026-10-02T06:54:23.546Z

Updated: 2026-10-02T18:00:20.505Z

Reserved: 2026-07-16T23:53:32.558Z

Link: CVE-2026-16000

cve-icon Vulnrichment

Updated: 2026-10-02T18:00:15.822Z

cve-icon NVD

Status : Analyzed

Published: 2026-10-02T07:16:36.400

Modified: 2026-10-27T16:32:54.857

Link: CVE-2026-16000

cve-icon Redhat

No data.