Open Zaak’s Documenten import task uses an attacker‑controlled CSV field called bestandspad without ensuring the resolved path stays inside the configured base directory. An application with an all‑authorizations token can supply a path that points to any file that the Celery worker can read. Those files are then copied into the shared document store and later retrieved through the standard document download API, exposing server secrets or private files to the token holder. This is a confidentiality breach in accordance with CWE‑200. The impact is that an attacker with sufficient token privileges can read arbitrary server files, including password files, logs, or configuration files, without needing additional system access.

The vulnerable code is present in the open‑zaak project, specifically in versions 1.13.0 through 1.27.2, 1.28.2, and 1.29.0. These releases expose the import_document_row function that handles the CSV upload. All builds of open‑zaak in this version range are affected until the issue is fixed in the referenced releases 1.27.2, 1.28.2, and 1.29.0.

The CVSS score of 6.8 indicates moderate severity. No EPSS score is currently available, and the issue is not listed in CISA’s KEV catalog, so the exploitation likelihood cannot be quantified. The attack path requires a valid application token with the all‑authorizations scope and the ability to send a CSV file to the import endpoint. Once a crafted path is submitted, the Celery worker copies the file to the document store, and the attacker can download it via the public download API, yielding the contents of any file readable by the worker. The vulnerability is fully mitigated by upgrading to the patched releases; otherwise, the only mitigations are to remove the all‑authorizations token or disable the import endpoint until a patch is applied.