Summary
A possible Remote Code Execution attack when using the Struts REST plugin with XStream handler to handle XML payloadsWho should read this | All Struts 2 developers and users |
---|---|
Impact of vulnerability | A RCE attack is possible because of a vulnerability in the XStream library |
Maximum security rating | Critical |
Recommendation | Upgrade to Struts 2.5.13 or Struts 2.3.34 |
Affected Software | Struts 2.3.7 - Struts 2.3.33, Struts 2.5 - Struts 2.5.12 |
Reporter | Man Yue Mo <mmo at semmle dot com> |
CVE Identifier | CVE-2017-9793 |
Problem
The REST Plugin is using a XStreamHandler
with an instance of XStream for deserialization without any type filtering and this can leads to Remote Code Execution when deserializing XML payloads.
Solution
Upgrade to Apache Struts version 2.5.13 or 2.3.34.
Backward compatibility
It is possible that some REST actions stop working because of applied default restrictions on available classes. In such case please investigate the new interfaces that was introduced to allow define class restrictions per action, those interfaces are:
org.apache.struts2.rest.handler.AllowedClasses
org.apache.struts2.rest.handler.AllowedClassNames
org.apache.struts2.rest.handler.XStreamPermissionProvider
Workaround
No workaround is possible, the best option is to remove the Struts REST plugin when not used or limit it to server normal pages and JSONs only:
<constant name="struts.action.extension" value="xhtml,,json" />