hsec-2026-0008
osv_haskell
Description
# 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 The older `x509` and `x509-validation` packages are also affected but are no longer maintained and have no fix available.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`.
Timeline
- Published
- unknown
- Last Modified
- unknown
CVSS Details
CVSS details not available.
Affected Products
No product information available.
References
Linked Vulnerabilities
No linked vulnerabilities found.
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"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's\npermitted subtrees. An attacker with access to a name-constrained\nsub-CA's private key could therefore issue certificates for domains\noutside the sub-CA's 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attacks on TLS connections.\n\nThe older `x509` and `x509-validation` packages are also affected but\nare no longer maintained and have no fix available.\n\nThis issue was fixed in `crypton-x509-validation-1.9.1` and\n`crypton-x509-1.9.1`.\n",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": "2026-06-03T13:45:42.872452373Z",
"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": "1.7.5",
"summary": "crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints"
}