OpenAM: Unauthenticated Remote Code Execution via Class.forName in AuthXMLUtils.createCustomCallback

Summary

A pre-authentication remote code execution vulnerability affects OpenAM. The remote authentication endpoint (/authservice, PLL) accepts an XML element that names an arbitrary Java class, which the server then loads and instantiates without validation. On a default configuration this is reachable without authentication and allows an attacker to run code on the server.

Impact

Unauthenticated remote code execution / full server compromise on any OpenAM instance with default settings.

Affected

All releases up to and including 16.1.1 (the defect predates the Open Identity Platform fork).

Remediation

Upgrade to 16.1.2. The fix resolves the class named in a <CustomCallback> element without running its static initialisers and rejects it unless it implements DSAMECallbackInterface, and it constrains deserialisation of the serialised Subject value to a class allowlist.

Interim mitigation

If you cannot upgrade immediately:

• Restrict or block external network access to /authservice. This is the only reliable mitigation.
• Optionally, block PLL requests carrying a <CustomCallback className="..."> element at the reverse proxy or WAF. That element is only produced for custom DSAMECallbackInterface callbacks, so most deployments never send it — confirm against your own traffic before enforcing.
• Enabling sunRemoteAuthSecurityEnabled does not mitigate this issue. The remote-auth security token is checked in AuthXMLHandler.processAuthXMLRequest, which runs only after AuthXMLRequest.parseXML has already parsed the request and instantiated the class named in the <CustomCallback className="..."> element. Do not rely on it as a substitute for upgrading or for network restriction.

Credit

Vulnerability discovered by Zhixi "Jace" Sun of ASM/VI at TikTok. Correction of the interim mitigation guidance contributed by @BarakSrour.