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hsec-2026-0008
Vulnerability from osv_haskell
Published
2026-06-03 13:30
Modified
2026-06-03 13:30
Summary
crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints
Details

crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints

The crypton-x509-validation and crypton-x509 libraries did not enforce the X.509 Name Constraints extension during certificate validation. The Name Constraints extension is a critical X.509 extension that restricts the namespace (permitted and excluded subtrees) for which a CA is authorized to issue certificates.

Without this enforcement, a TLS client would accept certificates with Subject Alternative Names (SANs) that fall outside the issuing CA's permitted subtrees. An attacker with access to a name-constrained sub-CA's private key could therefore issue certificates for domains outside the sub-CA's intended scope, enabling impersonation of arbitrary domains and man-in-the-middle attacks on TLS connections.

The older x509 and x509-validation packages are also affected but are no longer maintained and have no fix available.

This issue was fixed in crypton-x509-validation-1.9.1 and crypton-x509-1.9.1.

References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "human_link": "https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0008.md",
        "osv": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0008.json"
      },
      "package": {
        "ecosystem": "Hackage",
        "name": "crypton-x509-validation"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.6.12"
            },
            {
              "fixed": "1.9.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
          "type": "CVSS_V3"
        }
      ]
    },
    {
      "database_specific": {
        "human_link": "https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0008.md",
        "osv": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0008.json"
      },
      "package": {
        "ecosystem": "Hackage",
        "name": "crypton-x509"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.7.6"
            },
            {
              "fixed": "1.9.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
          "type": "CVSS_V3"
        }
      ]
    },
    {
      "database_specific": {
        "human_link": "https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0008.md",
        "osv": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0008.json"
      },
      "package": {
        "ecosystem": "Hackage",
        "name": "x509-validation"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
          "type": "CVSS_V3"
        }
      ]
    },
    {
      "database_specific": {
        "human_link": "https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0008.md",
        "osv": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0008.json"
      },
      "package": {
        "ecosystem": "Hackage",
        "name": "x509"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N",
          "type": "CVSS_V3"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-9648"
  ],
  "database_specific": {
    "home": "https://github.com/haskell/security-advisories",
    "osvs": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export",
    "repository": "https://github.com/haskell/security-advisories"
  },
  "details": "# crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints\n\nThe `crypton-x509-validation` and `crypton-x509` libraries did not\nenforce the X.509 Name Constraints extension during certificate\nvalidation. The Name Constraints extension is a critical X.509\nextension that restricts the namespace (permitted and excluded\nsubtrees) for which a CA is authorized to issue certificates.\n\nWithout this enforcement, a TLS client would accept certificates with\nSubject Alternative Names (SANs) that fall outside the issuing CA\u0027s\npermitted subtrees. An attacker with access to a name-constrained\nsub-CA\u0027s private key could therefore issue certificates for domains\noutside the sub-CA\u0027s intended scope, enabling impersonation of\narbitrary domains and man-in-the-middle attacks on TLS connections.\n\nThe older `x509` and `x509-validation` packages are also affected but\nare no longer maintained and have no fix available.\n\nThis issue was fixed in `crypton-x509-validation-1.9.1` and\n`crypton-x509-1.9.1`.\n",
  "id": "HSEC-2026-0008",
  "modified": "2026-06-03T13:30:48Z",
  "published": "2026-06-03T13:30:48Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.kb.cert.org/vuls/id/862559"
    },
    {
      "type": "FIX",
      "url": "https://github.com/kazu-yamamoto/crypton-certificate/pull/30"
    }
  ],
  "schema_version": "1.5.0",
  "summary": "crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints"
}



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