Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.3, pki.verifyCertificateChain() in lib/x509.js does not decode or enforce the X.509 nameConstraints extension while validating certificate paths. A name-constrained certificate authority with a non-critical extension can therefore issue a leaf certificate with a subjectAltName dNSName or subject commonName outside a permitted subtree or inside an excluded subtree, and node-forge accepts the chain. Exploitation requires a name-constrained CA that chains to a trusted root and either its private key or the ability to obtain an out-of-scope certificate, allowing impersonation of names outside the delegated namespace, including against forge.tls clients. Chains without nameConstraints are not affected, and affected versions safely reject critical nameConstraints as unsupported rather than accepting them. This issue is fixed in version 1.4.3.