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.

CVSS 3.1

9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 12% of CVEs (scores of 2026-10-25)

Published

2026-06-11

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

References

• https://github.com/haskell/security-advisories/pull/332
• 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://www.kb.cert.org/vuls/id/862559

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