Legion of the Bouncy Castle bc-csharp up to 2.6.x CCM CcmBlockCipher/KCcmBlockCipher missing encryption

Summaryinfo

A vulnerability was found in Legion of the Bouncy Castle bc-csharp up to 2.6.x and classified as problematic. This impacts the function CcmBlockCipher/KCcmBlockCipher of the component CCM. The manipulation results in missing encryption. This vulnerability is cataloged as CVE-2026-103601. The attack may be launched remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Legion of the Bouncy Castle bc-csharp up to 2.6.x. Affected is the function CcmBlockCipher/KCcmBlockCipher of the component CCM. The manipulation with an unknown input leads to a missing encryption vulnerability. CWE is classifying the issue as CWE-311. The product does not encrypt sensitive or critical information before storage or transmission. This is going to have an impact on confidentiality. CVE summarizes:

Release of unverified plaintext in the CCM (CcmBlockCipher) and DSTU 7624 CCM (KCcmBlockCipher) AEAD modes in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker to obtain decryptions of ciphertexts of their choosing via forged messages sent to an application that lets the output buffer of a failed decryption be observed, for example through buffer reuse or logging, because decryption wrote the recovered plaintext into the caller-supplied output buffer before checking the authentication tag and left it there when the check failed. Only decryption into a caller-supplied buffer is affected; methods that return a newly allocated array are not.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-103601 since 10/01/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1600.

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). Once again VulDB remains the best source for vulnerability data.

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

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion