CVE-2026-9648: CVE-2026-9648

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-11 · updated 2026-10-26

Description

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.

Affected products

Haskell Programming Language crypton-certificate: before 1.9.1 — fixed in 1.9.1

How to fix

Upgrade to a fixed version: Haskell Programming Language crypton-certificate 1.9.1. Check the vendor advisory for mitigations.

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

Get alerted when CVE-2026-9648 or the next vulnerability affects your stack