Legion of the Bouncy Castle bc-csharp up to 2.6.x CMP/CRMF Password-Based MAC Verifier PKMacBuilder allocation of resources

Summaryinfo

A vulnerability categorized as problematic has been discovered in Legion of the Bouncy Castle bc-csharp up to 2.6.x. This issue affects the function PKMacBuilder of the component CMP/CRMF Password-Based MAC Verifier. Executing a manipulation can lead to allocation of resources. This vulnerability is handled as CVE-2026-63568. The attack can be executed remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Legion of the Bouncy Castle bc-csharp up to 2.6.x. This vulnerability affects the function PKMacBuilder of the component CMP/CRMF Password-Based MAC Verifier. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect availability. CVE summarizes:

Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker to cause a denial of service through CPU exhaustion via a CMP message or CRMF certificate request whose PBMParameter declares a very large iteration count, because PKMacBuilder enforced its iteration-count ceiling only when the caller had supplied an explicit maximum through the PKMacBuilder(IPKMacPrimitivesProvider, int) constructor. With any other constructor, ProtectedPkiMessage.Verify and CertificateRequestMessage.IsValidSigningKeyPop performed as many hash iterations as the sender requested, up to about 2^31, before the MAC could be checked.

The advisory is available at github.com. This vulnerability was named CVE-2026-63568 since 07/17/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 2.7.0 eliminates this vulnerability.

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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

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CPE 2.2info

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