# CVE-2021-41131: Client metadata path-traversal

Source: https://junglewise.ai/threats/cve-2021-41131-client-metadata-path-traversal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-10-19  
License: CC BY 4.0 with a link back

CVE-2021-41131 · Severity: low · CVSS 3.1 · Published 2021-10-19

python-tuf is a Python reference implementation of The Update Framework (TUF). In both clients (`tuf/client` and `tuf/ngclient`), there is a path traversal vulnerability that in the worst case can overwrite files ending in `.json` anywhere on the client system on a call to `get_one_valid_targetinfo()`. It occurs because the rolename is used to form the filename, and may contain path traversal characters (ie `../../name.json`). The impact is mitigated by a few facts: It only affects implementations that allow arbitrary rolename selection for delegated targets metadata, The attack requires the ability to A) insert new metadata for the path-traversing role and B) get the role delegated by an existing targets metadata, The written file content is heavily restricted since it needs to be a valid, signed targets file. The file extension is always .json. A fix is available in version 0.19 or newer. There are no workarounds that do not require code changes. Clients can restrict the allowed character set for rolenames, or they can store metadata in files named in a way that is not vulnerable: neither of these approaches is possible without modifying python-tuf.

Technologies: [tuf (PyPI)](https://junglewise.ai/threats/technologies/tuf). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-41131 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-41131 being exploited in the wild.

**How severe is CVE-2021-41131?** Low severity, with a CVSS score of 3.1, published 19 October 2021.

**Which products and versions are affected?** tuf (PyPI) ECOSYSTEM:introduced=0,fixed=0.19.0, GIT:introduced=0,fixed=4ad7ae48fda594b640139c3b7eae21ed5155a102|ECOSYSTEM:introduced=0,fixed=0.19.0.

**Is there a fix for CVE-2021-41131?** Yes. tuf (PyPI): upgrade to 0.19.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-41131?** Check whether you run tuf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- tuf (PyPI): upgrade to 0.19.0 or later

  ```sh
  pip install "tuf>=0.19.0"
  ```


## Affected products

- tuf (PyPI) ECOSYSTEM:introduced=0,fixed=0.19.0, GIT:introduced=0,fixed=4ad7ae48fda594b640139c3b7eae21ed5155a102|ECOSYSTEM:introduced=0,fixed=0.19.0

## Identifiers

- CVE-2021-41131
- GHSA-wjw6-2cqr-j4qr
- PYSEC-2021-376

## Related threats

- [theupdateframework python-tuf improper case sensitivity in delegation matching](https://junglewise.ai/threats/theupdateframework-python-tuf-improper-case-sensitivity-in-delegation-4289ebd1)
- [tuf's Metadata API: Targets.get_delegated_role() is missing input validation](https://junglewise.ai/threats/tuf-s-metadata-api-targets-get-delegated-role-is-missing-input-88281f97)
- [Python-TUF vulnerable to incorrect threshold signature computation for new root metadata](https://junglewise.ai/threats/python-tuf-vulnerable-to-incorrect-threshold-signature-computation-for-042f316e)
- [Invalid root may become trusted root in The Update Framework (TUF)](https://junglewise.ai/threats/cve-2020-15163-invalid-root-may-become-trusted-root-in-the-update-framework-tuf)
- [PYSEC-2020-147 - TUF (aka The Update Framework) through 0.12.1 has Improper Verification of a Cryptographic Signature.](https://junglewise.ai/threats/cve-2020-6174-incorrect-threshold-signature-computation-in-tuf)