Crypton Certificate
Monthly
Certificate impersonation in the crypton-x509-validation Haskell library (versions 1.6.12 through 1.9.0, and the paired crypton-x509 from 1.7.6) lets a TLS client accept certificates whose Subject Alternative Names lie outside an issuing sub-CA's permitted subtrees, because the X.509 NameConstraints extension was never evaluated during chain validation. An adversary holding a name-constrained sub-CA key can mint certificates for arbitrary domains and mount man-in-the-middle attacks against clients built on these libraries. There is no public exploit identified at time of analysis and EPSS is very low (0.02%), but a vendor patch (1.9.1) exists and the source fix is public, tracked as CERT/CC VU#862559 and HSEC-2026-0008.
Certificate impersonation in the crypton-x509-validation Haskell library (versions 1.6.12 through 1.9.0, and the paired crypton-x509 from 1.7.6) lets a TLS client accept certificates whose Subject Alternative Names lie outside an issuing sub-CA's permitted subtrees, because the X.509 NameConstraints extension was never evaluated during chain validation. An adversary holding a name-constrained sub-CA key can mint certificates for arbitrary domains and mount man-in-the-middle attacks against clients built on these libraries. There is no public exploit identified at time of analysis and EPSS is very low (0.02%), but a vendor patch (1.9.1) exists and the source fix is public, tracked as CERT/CC VU#862559 and HSEC-2026-0008.