SummaryUpgrade Commons FileUpload to version 1.3.1 (avoids DoS attacks) and adds 'class' to exclude params in ParametersInterceptor (avoid ClassLoader manipulation)
Who should read this
All Struts 2 developers and users
Impact of vulnerability
DoS attacks and ClassLoader manipulation
Maximum security rating
Developers should immediately upgrade to Struts 18.104.22.168
Struts 2.0.0 - Struts 22.214.171.124
Peter Magnusson (peter.magnusson at omegapoint.se), Przemysław Celej (p-celej at o2.pl)
CVE-2014-0050 (DoS), CVE-2014-0094 (ClassLoader manipulation)
The default upload mechanism in Apache Struts 2 is based on Commons FileUpload version 1.3 which is vulnerable and allows DoS attacks. Additional ParametersInterceptor allows access to 'class' parameter which is directly mapped to getClass() method and allows ClassLoader manipulation.
In Struts 126.96.36.199, Commons FileUpload was updated to version 1.3.1 and "class" was added to excludeParams in struts-default.xml configuration of ParametersInterceptor.
No backward compatibility problems are expected.
If you cannot upgrade to version 188.8.131.52 which is strongly advised, you can apply below workarounds:
The fixed commons-fileupload library is a drop-in replacement for the vulnerable version. Deployed applications can be hardened by replacing the commons-fileupload jar file in WEB-INF/lib with the updated jar. For Maven
based Struts 2 projects, the following dependency needs to be added:
Exclude 'class' parameter
Simple add '^class\.*' to the list of excludeParams as below