Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.3, a forge.tls client can pass a handshake record to tls.handleHandshake() while the connection has no session, including after a close_notify alert, after the application calls close(), or before handshake() is called. The handler dereferences c.session.md5 before dispatching the message, causing a TypeError to propagate from connection.process(). A malicious server or on-path attacker can deliver the record, including after a reset when the connection uses no encryption, and terminate a Node.js process if the application does not catch the exception. forge.tls servers are not affected, and there is no confidentiality or integrity impact. This issue is fixed in version 1.4.3.