In MISP, the OrganisationsController::__uploadLogo method processed a caller-supplied tmp_name value with filesystem probes (file_exists, MIME type detection, EXIF reading) before verifying that the value corresponded to a genuine PHP file upload via is_uploaded_file. An authenticated site-admin user could supply an arbitrary server file path as the tmp_name parameter. The application would then probe that path and return distinct validation error messages depending on whether the file existed and what its image type was, effectively creating a file-existence and image-type oracle against the server filesystem.
The vulnerability requires site-admin privileges and does not allow arbitrary file read, code execution, or modification; the impact is limited to disclosure of whether a given path exists on the server and, for image files, their type.