CVE-2026-9648

The crypton-x509-validation Haskell library fails to enforce X.509 NameConstraints, allowing TLS clients to accept certificates whose Subject Alternative Names fall outside the issuing CA’s permitted subtrees. This oversight enables an attacker who compromises a name-constrained sub-CA to impersonate domains beyond its intended scope.

Score

CVSS 3.1 9.1 Critical

Status

Deferred - cret@cert.org

Published

2026-06-11

Last modified

2026-10-26

Affected products

• Crypton-certificate (Haskell Programming Language)

References

• https://github.com/kazu-yamamoto/crypton-certificate/pull/30
• https://github.com/kazu-yamamoto/crypton-certificate/pull/30/changes/f4b77edf6ead77f4a886da40e41eab20f0180e39
• https://hackage.haskell.org/package/crypton-x509-validation-1.9.1/revisions/
• https://github.com/haskell/security-advisories/pull/332
• https://www.kb.cert.org/vuls/id/862559