Legion of the Bouncy Castle bc-csharp up to 2.6.x CCM mode implementation KCcmBlockCipher flags missing encryption

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Legion of the Bouncy Castle bc-csharp up to 2.6.x. Affected by this vulnerability is the function KCcmBlockCipher of the component CCM mode implementation. The manipulation of the argument flags leads to missing encryption. This vulnerability is listed as CVE-2026-16000. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Legion of the Bouncy Castle bc-csharp up to 2.6.x. It has been rated as problematic. This issue affects the function KCcmBlockCipher of the component CCM mode implementation. The manipulation of the argument flags with an unknown input leads to a missing encryption vulnerability. Using CWE to declare the problem leads to CWE-311. The product does not encrypt sensitive or critical information before storage or transmission. Impacted is confidentiality. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-16000 since 07/17/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1600 for this issue.

Upgrading to version 2.7.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-3713). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Open Source Bouncy Castle

Productinfo

Vendor

• Legion of the Bouncy Castle

Name

• bc-csharp

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6

CPE 2.3info

• 🔒
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CPE 2.2info

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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