An attacker can manipulate file upload params to enable paths traversal and under some circumstances this can lead to uploading a malicious file which can be used to perform Remote Code Execution. Users are recommended to upgrade to versions Struts 2.5.33 or Struts 6.3.0.2 or greater to fix this issue.
When a Multipart request is performed but some of the fields exceed the maxStringLength limit, the upload files will remain in struts.multipart.saveDir even if the request has been denied. Users are recommended to upgrade to versions Struts 2.5.32 or 6.1.2.2 or Struts 6.3.0.1 or greater, which fixe this issue.
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.
Forced OGNL evaluation, when evaluated on raw user input in tag attributes, may lead to remote code execution.
In the Convention plugin in Apache Struts, it is possible to prepare a special URL which will be used for path traversal and execution of arbitrary code on server side.