Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.1, node-forge enforced an X.509 CA certificate's basicConstraints.pathLenConstraint only when that certificate also carried a keyUsage extension. Exploitation requires a path-length-constrained CA without keyUsage that chains to a root trusted by the application, and an attacker who holds that CA's private key or obtains a subordinate CA certificate from it. The attacker could then construct a chain exceeding the declared path length that still passed pki.verifyCertificateChain(). Public web PKI CA certificates normally include keyUsage; private PKIs with CA certificates created without it are more likely to be affected. This issue is fixed in version 1.4.1.