CVE-2026-55825

Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in Contao ausnutzen, um Informationen offenzulegen.

## Summary An authenticated backend user who can access one job can request an attachment identifier containing `../` segments and make the job attachment download endpoint read a file from another job directory inside `var/job-attachments`. The controller authorizes only the `jobUuid` route parameter. The later attachment lookup joins that authorized job UUID with the attacker-controlled `identifier`, then passes the combined path to the virtual filesystem. `VirtualFilesystem::resolve()` canonicalizes the whole path and only rejects paths that escape the filesystem mount, so `authorized-job/../victim-job/debug_log.csv` becomes `victim-job/debug_log.csv`. This is a cross-job authorization bypass for known job attachment paths. It is not a practical brute-force against unknown jobs because job directories are UUID v4 values. ## Root Cause `JobsController::downloadJobAttachment()` checks access to the route `jobUuid` before loading the attachment: ```php $job = $this->jobs->getByUuid($jobUuid); if (!$job || !$this->jobs->hasAccess($job)) { throw $this->createNotFoundException(); } $attachment = $this->jobs->getAttachment($jobUuid, $identifier); ``` `Jobs::getAttachment()` then resolves a path built from the authorized job UUID and the attacker-controlled identifier: ```php $fileItem = $this->jobAttachmentsStorage->get($this->getAttachmentIdentifier($job, $identifier)); ``` ```php return $job->getUuid().'/'.$identifier; ``` `VirtualFilesystem::resolve()` canonicalizes the combined path. It rejects absolute paths and paths that start with `..`, but it does not preserve the authorized job directory as a boundary: ```php $path = Path::canonicalize($location); if (str_starts_with($path, '..')) { throw new \OutOfBoundsException(...); } return Path::join($this->prefix, $path); ``` Therefore: ```text <authorized-job>/../<victim-job>/debug_log.csv ``` canonicalizes to: ```text <victim-job>/debug_log.csv ``` which remains inside the `job-attachments` filesystem mount and is accepted. ## Recommended Fix Treat the attachment identifier as a filename, not a path: - Reject `/`, `\`, NUL, and dot-segment components in `identifier`. - Add a route requirement that prevents slashes in `{identifier}` if nested attachment paths are not intended. - After resolving, assert the canonical relative path starts with `<authorized-job-uuid>/` before returning a `FilesystemItem`. - Apply the same identifier validation in `Jobs::addAttachment()` so future producers/extensions cannot write outside the owning job directory. ### Impact A low-privileged backend user can read another job's attachment if they know or obtain the target job UUID and attachment filename. Built-in crawler jobs attach CSV logs such as `debug_log.csv`, `broken-link-checker_log.csv`, and `search-index_log.csv`, which can contain crawled URLs, referring URLs, tags, and error messages.