ParametersInterceptor in OpenSymphony XWork 2.0.x before 2.0.6 and 2.1.x before 2.1.2, as used in Apache Struts and other products, does not properly restrict # (pound sign) references to context objects, which allows remote attackers to execute Object-Graph Navigation Language (OGNL) statements and modify server-side context objects, as demonstrated by use of a \u0023 representation for the # character.

Struts support in OpenSymphony XWork before 1.2.3, and 2.x before 2.0.4, as used in WebWork and Apache Struts, recursively evaluates all input as an Object-Graph Navigation Language (OGNL) expression when altSyntax is enabled, which allows remote attackers to cause a denial of service (infinite loop) or execute arbitrary code via form input beginning with a "%{" sequence and ending with a "}" character.