Arbitrary Code Execution via File Upload in ExpressionEngine

CVE-2020-13443 · HIGH Severity

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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).

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