In MISP, the EventReport::uploadPicture method in processed a caller-supplied tmp_name field by invoking file_exists(), mime_content_type(), and exif_imagetype() on the supplied path before verifying that the value was a genuine PHP upload via is_uploaded_file(). An authenticated user holding the perm_add permission could supply an arbitrary filesystem path as the tmp_name value. The application would then probe that path and return distinct validation error messages depending on whether the file existed, its MIME type, or its image format. By observing the differing error responses, an attacker could enumerate the existence of files at arbitrary paths on the MISP server and determine their type.
This constitutes an information disclosure vulnerability: the server's filesystem layout and file types are leaked to any user with the perm_add role without requiring administrative access.
The vulnerability does not allow reading file contents, writing files, or executing code, but it can aid further attacks by revealing sensitive file locations (e.g., configuration files, private keys, or other artifacts) present on the host.