Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion
Summary
| CVE | CVE-2026-63568 |
|---|---|
| State | PUBLISHED |
| Assigner | bcorg |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-02 07:16:37 UTC |
| Updated | 2026-10-27 16:05:42 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 8.7 HIGH from 91579145-5d7b-4cc5-b925-a0262ff19630
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:X/V:X/RE:X/U:X
EPSS: 0.003190000 probability, percentile 0.246910000 (date 2026-10-27)
Problem Types: CWE-770 | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 91579145-5d7b-4cc5-b925-a0262ff19630 | Secondary | 8.7 | HIGH | 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/C... |
| 4.0 | CNA | CVSS | 8.7 | HIGH | 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 |
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v4.0 Breakdown
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:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Bouncycastle | Bc-csharp | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Legion Of The Bouncy Castle Inc. | Bc-csharp | affected 2.7.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/bcgit/bc-csharp/commit/65283bae66843d0d3c13c5e0272dbbe1c0d6aa04 | 91579145-5d7b-4cc5-b925-a0262ff19630 | github.com | Patch |
| github.com/bcgit/bc-csharp/commit/d16f08a53dd0a78eb3310bbe80c947c7e1677290 | 91579145-5d7b-4cc5-b925-a0262ff19630 | github.com | Patch |
| github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63 | 91579145-5d7b-4cc5-b925-a0262ff19630 | github.com | Patch |
| github.com/bcgit/bc-csharp/wiki/CVE-2026-63568 | 91579145-5d7b-4cc5-b925-a0262ff19630 | github.com | Patch, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research. (en)