Apache Struts vulnerabilities CVE-2020-17530 and CVE-2021-31805

• CVE-2020-17530
  Forced OGNL evaluation, when evaluated on raw user input in tag attributes, may lead to remote code execution. Affected software : Apache Struts 2.0.0 - Struts 2.5.25.
• CVE-2021-31805
  The fix issued for CVE-2020-17530 was incomplete. So from Apache Struts 2.0.0 to 2.5.29, still 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.

Impact

Using a forced Object-Graph Navigation Language (OGNL) evaluation on untrusted user input allows an attacker to perform remote code execution leading to security degradation.