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Vulnerability record · CVE-2026-63568 · published 2 October 2026

CVE-2026-63568: Bouncycastle bc-csharp allocation without limits vulnerability

Bouncycastle · Bc Csharp

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.

8.7 CVSS 4.0 High EPSS 0.36% · top 69.4% CWE-770 · Allocation without limits
8.7CVSS 4.0 base score
0.36%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
27 Oct 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63 Patch
https://github.com/bcgit/bc-csharp/commit/65283bae66843d0d3c13c5e0272dbbe1c0d6aa04 Patch
https://github.com/bcgit/bc-csharp/commit/d16f08a53dd0a78eb3310bbe80c947c7e1677290 Patch
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63568 PatchVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.1CVE-2026-63569Bouncycastle bc-csharp improper input validation vulnerabilityImproper input validation in DHAgreement.CalculateAgreement (MTI/A0 two-pass Diffie-Hellman) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7…EPSS 0.33%8.7CVE-2026-63574Bouncycastle bc-csharp vulnerabilityMemory allocation with excessive size value in the OpenPGP signature and user attribute subpacket parsers (SignatureSubpacketsParser.ReadPacket, User…EPSS 0.43%8.7CVE-2026-63571Bouncycastle bc-csharp improper verification of cryptographic signature vulnerabilityImproper verification of cryptographic signature in the attribute certificate path validator (PkixAttrCertPathValidator, also used by PkixAttrCertPat…EPSS 0.14%8.7CVE-2026-103600Bouncycastle bc-csharp vulnerabilityUncontrolled recursion in the ASN.1 parser (Asn1InputStream, Asn1StreamParser) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a re…EPSS 0.36%8.7CVE-2026-103603Bouncycastle bc-csharp vulnerabilityMemory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. …EPSS 0.52%8.7CVE-2026-103604Bouncycastle bc-csharp vulnerabilityInefficient algorithmic complexity in X.509 distinguished name string conversion (X509Name.ToString and IetfUtilities.ValueToString) in Legion of the…EPSS 0.32%8.7CVE-2026-63566Bouncycastle bc-csharp vulnerabilityMemory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle …EPSS 0.43%8.7CVE-2026-16000Bouncycastle bc-csharp vulnerabilityMissing cryptographic step in the DSTU 7624 CCM mode implementation (KCcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allo…EPSS 0.22%

Source: NIST National Vulnerability Database (record CVE-2026-63568), CISA KEV, FIRST EPSS (scores of 2026-11-14). This page is refreshed as NVD updates the record.