GHSA-grm4-wm43-9jh5: Contao: Possible path traversal in job download URIs

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: $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: $fileItem = $this->jobAttachmentsStorage->get($this->getAttachmentIdentifier($job, $identifier)); 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: $path = Path::canonicalize($location); if (str_starts_with($path, '..')) { throw new \OutOfBoundsException(...); } return Path::join($this->prefix, $path); Therefore: <authorized-job>/../<victim-job>/debug_log.csv canonicalizes to: <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 pa