CVE-2026-107844

Ein Angreifer kann mehrere Schwachstellen in Contao ausnutzen, um Sicherheitsmaßnahmen zu umgehen, Berechtigungen zu erweitern und möglicherweise Administratorrechte zu erlangen, Cross-Site-Scripting-Angriffe durchzuführen, sensible Informationen offenzulegen und Daten zu manipulieren.

`ImagesController` joins the user controlled `{path}` onto the configured image target directory with `Path::join()`, which canonicalises `..` segments, and never calls `Path::isBasePath()` to confirm the result stayed inside that directory. An unauthenticated GET with percent encoded dot segments therefore escapes the directory and the file is returned by `BinaryFileResponse`. Reads are bounded to the extensions in `contao.image.valid_extensions`, and paths below the upload directory fail for an unrelated reason, so this is reported as a missing boundary check rather than as a general arbitrary file read. Both Apache with the shipped `public/.htaccess` and nginx with the documented configuration are affected. ### Impact Any unauthenticated visitor can read files that are deliberately kept outside the document root, anywhere under the project directory, as long as the name ends in one of `contao.image.valid_extensions` (`jpg`, `jpeg`, `gif`, `png`, `tif`, `tiff`, `bmp`, `svg`, `svgz`, `webp`). The route also acts as an existence oracle for arbitrary paths, and on a debug enabled instance the 404 message discloses the absolute filesystem path. **Honesty caveat, stated because it lowers the severity.** The reporter could not use this to read protected member folders: every path below the upload directory returns 500 for the reason given under Details, so the practically reachable set is image typed files outside `files/`.