High · CVSS 8.7CVE-2026-63568

Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion

Answer in brief

CVE-2026-63568 records a High severity (CVSS 8.7) vulnerability in Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion. The current sources do not mark it as known exploited. The current feed maps Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 2, 2026Updated Oct 2, 2026Source checked Oct 2, 2026First seen by HOL Oct 2, 2026Material review Oct 2, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Legion of the Bouncy Castle Inc./BouncyCastle.Cryptographygeneric	>=0 <2.7.0	2.7.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography.
Review the reported fix. Update Legion of the Bouncy Castle Inc./BouncyCastle.Cryptography to 2.7.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 2, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 2, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 2, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.