THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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A possible Remote Code Execution attack when using an unintentional expression in Freemarker tag instead of string literals |
Who should read this | All Struts 2 developers and users |
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Impact of vulnerability | A RCE attack is possible when developer is using wrong construction in Freemarker tags |
Maximum security rating | CriticalModerate |
Recommendation | Upgrade to Struts 2.5.12 or Struts 2.3.34 |
Affected Software | Struts 2.0.1 .2 - Struts 2.3.33, Struts 2.5 - Struts 2.5.10 |
Reporter | Lupin <lupin1314 at gmail dot com> - jd.com security team |
CVE Identifier |
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Problem
The REST Plugin is using a XStreamHandler with an instance of XStream for deserialization without any type filtering and this can lead to Remote Code Execution when deserializing XML payloads.
Solution
When using expression literals or forcing expression in Freemarker tags (see example below) and using request values can lead to RCE attack.
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<@s.hidden name="redirectUri" value=redirectUri />
<@s.hidden name="redirectUri" value="${redirectUri}" /> |
In both cases a writable property is used in the value attribute and in both cases is threatened as an expression by Freemarker
Solution
Do not use such constructions in your code or use read-only properties to initialise the value attribute (property with getter only). Upgrade Upgrade to Apache Struts version 2.5.13 12 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.AllowedClassesorg.apache.struts2.rest.handler.AllowedClassNamesorg.apache.struts2.rest.handler.XStreamPermissionProvider
Workaround
The best option is to remove the Struts REST plugin when not used. Alternatively you can only upgrade the plugin by dropping in all the required JARs (plugin plus all dependencies). Another options is to limit th plugin to server normal pages and JSONs only:
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<constant name="struts.action.extension" value="xhtml,,json" /> |
No backward incompatibility issues are expected.
Workaround
Inspect your code and remove vulnerable constructions.