CVE-2026-9648
crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints
Published Jun 3, 2026 · updated Jun 3, 2026
# crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints The and 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 The older and packages are also affected but are no longer maintained and have no fix available. This issue was fixed in and .
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Jun 3, 2026 · OSV.dev
Detected
# crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints The and 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 wo
Jun 3, 2026 · OSV.dev
Fix available
crypton-x509-validation fixed in 1.9.1; crypton-x509 fixed in 1.9.1
Jun 3, 2026 · OSV.dev
Fix available
crypton-x509-validation fixed in 1.9.1
Jun 3, 2026 · OSV.dev
Fix available
crypton-x509 fixed in 1.9.1
Jun 3, 2026 · OSV.dev
Updated
# crypton-x509-validation and crypton-x509 do not enforce X.509 Name Constraints The and 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 wo
Affected
- Hackage crypton-x5091.7.6 → 1.9.1
- Hackage crypton-x509-validation1.6.12 → 1.9.1
- Hackage x5091.4.0, 1.4.1, 1.4.10
- Hackage x509-validation1.4.0, 1.4.1, 1.4.2