Vulnerability-Lookup

GHSA-MM8P-P4G9-932C

Vulnerability from github – Published: 2026-10-02 09:31 – Updated: 2026-10-02 09:31

Details

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.

Severity

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-63568"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-02T07:16:37Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-mm8p-p4g9-932c",
  "modified": "2026-10-02T09:31:17Z",
  "published": "2026-10-02T09:31:17Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63568"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-csharp/commit/65283bae66843d0d3c13c5e0272dbbe1c0d6aa04"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-csharp/commit/d16f08a53dd0a78eb3310bbe80c947c7e1677290"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63568"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-63568 (GCVE-0-2026-63568)

Vulnerability from cvelistv5 – Published: 2026-10-02 06:59 – Updated: 2026-10-02 18:11

Title

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

Summary

Severity

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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-02 18:11 UTC

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

bcorg mitre root Scorecard

References

4 references

URL	Tags
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63568	vendor-advisory
https://github.com/bcgit/bc-csharp/commit/10a9862…	patch
https://github.com/bcgit/bc-csharp/commit/65283ba…	patch
https://github.com/bcgit/bc-csharp/commit/d16f08a…	patch

Impacted products

1 product

Vendor	Product	Version
Legion of the Bouncy Castle Inc.	bc-csharp	Affected: 0 , < 2.7.0 (semver)

Credits

Discovered by Claude, Anthropic's AI assistant, and triaged by the Anthropic security team in collaboration with Anthropic Research.

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JSON

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{
  "containers": {
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            "other": {
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                "id": "CVE-2026-63568",
                "options": [
                  {
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                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-02T18:11:16.195048Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-02T18:11:27.486Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://www.nuget.org/packages/BouncyCastle.Cryptography",
          "defaultStatus": "unaffected",
          "packageName": "BouncyCastle.Cryptography",
          "product": "bc-csharp",
          "programFiles": [
            "crypto/src/crmf/PKMacBuilder.cs",
            "crypto/src/cmp/ProtectedPkiMessage.cs",
            "crypto/src/crmf/CertificateRequestMessage.cs"
          ],
          "repo": "https://github.com/bcgit/bc-csharp",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "versions": [
            {
              "lessThan": "2.7.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
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          "type": "finder",
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        }
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      "impacts": [
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      "metrics": [
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            "Recovery": "NOT_DEFINED",
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            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
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            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
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          "scenarios": [
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      "providerMetadata": {
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          "url": "https://github.com/bcgit/bc-csharp/commit/10a9862fad04bb0c832a78b10e71d9818d6d1a63"
        },
        {
          "tags": [
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      ],
      "source": {
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      },
      "title": "Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion",
      "x_antReportIds": [
        "ANT-2026-BS6SFW9B",
        "ANT-2026-SGFCCBWB"
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    "assignerShortName": "bcorg",
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    "datePublished": "2026-10-02T06:59:30.557Z",
    "dateReserved": "2026-07-16T23:48:46.076Z",
    "dateUpdated": "2026-10-02T18:11:27.486Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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GHSA-MM8P-P4G9-932C

CVE-2026-63568 (GCVE-0-2026-63568)

Tags

Sightings

Nomenclature

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