DUE TO SPAM, SIGN-UP IS DISABLED. Goto Selfserve wiki signup and request an account.
Summary
| Excerpt |
|---|
ParameterInterceptor vulnerability allows remote command execution |
Who should read this | All Struts 2 developers |
|---|---|
Impact of vulnerability | Remote command execution |
Maximum security rating | Critical |
Recommendation | Developers should immediately upgrade to Struts 2.3.1.2 or read the following solution instructions carefully for a configuration change to mitigate the vulnerability |
Affected Software | Struts 2.0.0 - Struts 2.3.1.1 |
Reporter | Meder Kydyraliev, Google Security Team |
CVE Identifier |
Problem
OGNL provides, among other features, extensive expression evaluation capabilities. The vulnerability allows a malicious user to bypass all the protections (regex pattern, deny method invocation) built into the ParametersInterceptor, thus being able to inject a malicious expression in any exposed string variable for further evaluation.
...
- #context - OgnlContext, the one guarding method execution based on 'xwork.MethodAccessor.denyMethodExecution' property value.
- #_memberAccess - SecurityMemberAccess, whose 'allowStaticAccess' field prevented static method execution.
- #root
- #this
- #_typeResolver
- #_classResolver
- #_traceEvaluations
- #_lastEvaluation
- #_keepLastEvaluation
Solution
The regex pattern inside the ParameterInterceptor was changed to provide a more narrow space of acceptable parameter names.
Furthermore the new setParameter method provided by the value stack will allow no more eval expression inside the param names.
...
In case an upgrade isn't possible in a particular environment, there is a configuration based mitigation workaround:
Possible Mitigation Workaround: Configure ParametersIntercptor in struts.xml to Exclude Malicious Parameters
The following additional interceptor-ref configuration, suggested by John Wilander, should mitigate the problem when applied correctly:
...