EXECUTIVE SUMMARY:
CVE-2026-9648 with a CVSS score of 9.1 is a critical vulnerability in the crypton-x509-validation Haskell library, specifically impacting all prior versions, which fails to enforce X.509 NameConstraints, a crucial certificate safeguard defined in RFC 5280, allowing attackers to forge trusted certificates by exploiting the missing check for NameConstraints, which tell a certificate authority exactly which domains it may cover. An attacker can exploit this vulnerability by compromising a name-constrained sub-CA, breaking out of its intended scope, and minting certificates for domains they were never authorized to cover, requiring access to a compromised sub-CA and some victim interaction, via a malicious server set up to lure Haskell clients, resulting in the attacker gaining full session visibility, including the ability to capture credentials, secrets, and sensitive traffic in transit. The business impact and consequences of a successful attack can be severe, including exposure of sensitive financial information, credential theft, and secret theft, particularly in delegated PKI setups commonly used by financial firms, and prerequisites for exploitation include a compromised sub-CA and some level of victim interaction, making this vulnerability especially dangerous for organizations relying on Haskell backends.[/subscribe_to_unlock_form]
EXECUTIVE SUMMARY:
CVE-2026-9648 with a CVSS score of 9.1 is a critical vulnerability in the crypton-x509-validation Haskell library, specifically impacting all prior versions, which fails to enforce X.509 NameConstraints, a crucial certificate safeguard defined in RFC 5280, allowing attackers to forge trusted certificates by exploiting the missing check for NameConstraints, which tell a certificate authority exactly which domains it may cover. An attacker can exploit this vulnerability by compromising a name-constrained sub-CA, breaking out of its intended scope, and minting certificates for domains they were never authorized to cover, requiring access to a compromised sub-CA and some victim interaction, via a malicious server set up to lure Haskell clients, resulting in the attacker gaining full session visibility, including the ability to capture credentials, secrets, and sensitive traffic in transit. The business impact and consequences of a successful attack can be severe, including exposure of sensitive financial information, credential theft, and secret theft, particularly in delegated PKI setups commonly used by financial firms, and prerequisites for exploitation include a compromised sub-CA and some level of victim interaction, making this vulnerability especially dangerous for organizations relying on Haskell backends.[emaillocker id="1283"]
RECOMMENDATION:
We recommend you to update crypton-x509-validation to version 1.9.1.
REFERENCES:
The following reports contain further technical details:
https://securityonline.info/haskell-tls-vulnerability-cve-2026-9648/