ExpressionEngine before 5.3.2 allows remote attackers to upload and execute...

Vulnerability Description

ExpressionEngine before 5.3.2 allows remote attackers to upload and execute arbitrary code in a .php%20 file via Compose Msg, Add attachment, and Save As Draft actions. A user with low privileges (member) is able to upload this. It is possible to bypass the MIME type check and file-extension check while uploading new files. Short aliases are not used for an attachment; instead, direct access is allowed to the uploaded files. It is possible to upload PHP only if one has member access, or registration/forum is enabled and one can create a member with the default group id of 5. To exploit this, one must to be able to send and compose messages (at least).

References

• https://expressionengine.com/blog
• https://gist.github.com/mariuszpoplwski/51604d8a6d7d78fffdf590c25e844e09