CVE-2026-63568

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.

• CWE-770

• https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63Patch
• https://github.com/bcgit/bc-csharp/commit/65283bae66843d0d3c13c5e0272dbbe1c0d6aa04Patch
• https://github.com/bcgit/bc-csharp/commit/d16f08a53dd0a78eb3310bbe80c947c7e1677290Patch
• https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63568Patch, Vendor Advisory

Published

Oct 2, 2026

Last Modified

Oct 27, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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