Improper X.509 NameConstraints Enforcement in crypton-x509-validation
CVE-2026-9648 affects the Haskell crypton-x509-validation library. The vulnerability is caused by the library failing to enforce X.509 NameConstraints during certificate validation, a safeguard defined in RFC 5280. As a result, TLS clients using the library may accept certificates whose Subject Alternative Names fall outside the issuing CA’s permitted subtrees. This breaks the intended restriction model for name-constrained subordinate certificate authorities and allows certificates to validate even when they exceed the CA’s authorized namespace.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A certificate validation vulnerability in the Haskell crypton-x509-validation library caused by failure to enforce X.509 NameConstraints, allowing TLS clients to trust certificates outside the issuing CA’s permitted scope.
A vulnerability in the crypton-x509-validation Haskell library where X.509 NameConstraints are not enforced, allowing acceptance of certificates outside permitted subtrees and enabling broader domain impersonation if a constrained sub-CA is compromised.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.