MaterialX Stack Overflow via Lack of MTLX XML Parsing Recursion Limit

MaterialX is an open standard for the exchange of rich material and look-development content across applications and renderers. In versions 1.39.2 and below, when parsing an MTLX file with multiple nested nodegraph implementations, the MaterialX XML parsing logic can potentially crash due to stack exhaustion. An attacker could intentionally crash a target program that uses OpenEXR by sending a malicious MTLX file. This is fixed in version 1.39.3.