Apache Struts 2: CVE-2020-17530: Potential RCE when using forced evaluation

[Lukasz Lenart <lukaszlenart () apache org>]

Forced OGNL evaluation, when evaluated on raw user input in tag
attributes, may lead to remote code execution.

Problem
Some of the tag's attributes could perform a double evaluation if a
developer applied forced OGNL evaluation by using the %{...} syntax.
Using forced OGNL evaluation on untrusted user input can lead to a
Remote Code Execution and security degradation.

Solution
Avoid using forced OGNL evaluation on untrusted user input, and/or
upgrade to Struts 2.5.26 which checks if expression evaluation won't
lead to the double evaluation.

Please read our Security Bulletin for more details:
https://cwiki.apache.org/confluence/display/WW/S2-061

This vulnerability was identified by:
- Alvaro Munoz - pwntester at github dot com
- Masato Anzai of Aeye Security Lab, inc.

All developers are strongly advised to perform this action.


Kind regards
-- 
Łukasz
+ 48 606 323 122 http://www.lenart.org.pl/