# theupdateframework python-tuf improper case sensitivity in delegation matching

Source: https://junglewise.ai/threats/theupdateframework-python-tuf-improper-case-sensitivity-in-delegation-4289ebd1  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-28. Updated: 2026-05-28  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4 · Published 2026-05-28

The python-tuf library, which provides a framework for secure software updates, contains a vulnerability in how it validates file paths on Windows systems. Due to inconsistent handling of uppercase and lowercase letters, an attacker who controls a specific update role could potentially bypass security restrictions to provide unauthorized software updates. This could lead to the installation of untrusted software on Windows-based client machines.

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

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4, published 28 May 2026.

**Which products and versions are affected?** tuf (PyPI) <= 6.0.0; The Update Framework Project The Update Framework <= 6.0.0.

**Is there a fix for This vulnerability?** A patch was published on 2026-05-28: Fixed in version 7.0.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked with local access, in a software library.

**Am I affected?** Check whether you run tuf (PyPI) or The Update Framework Project The Update Framework 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.

## Technical details

The vulnerability exists in the `DelegatedRole._is_target_in_pathpattern` function within `tuf/api/_payload.py`. It utilizes Python's `fnmatch.fnmatch`, which internally calls `os.path.normcase()`. On Windows, this causes path patterns to be lowercased, leading to case-insensitive matching that violates the TUF specification. An attacker controlling a delegated role with a case-colliding path pattern (e.g., 'Foo/*' vs 'foo/*') can intercept requests intended for a legitimate role if their role is ordered earlier in the delegation walk. This issue is specific to Windows clients and has been fixed in version 7.0.0 by switching to `fnmatch.fnmatchcase`.

## Affected products

- theupdateframework tuf <= 6.0.0

## Timeline

- 2026-05-18: disclosed: Advisory first published on GitHub
- 2026-05-28: advisory: Advisory reviewed and updated on GitHub
- 2026-05-28: patched: Fixed in version 7.0.0

## References

- [https://api.github.com/users/kodareef5](https://api.github.com/users/kodareef5)
- [https://github.com/kodareef5](https://github.com/kodareef5)
- [https://api.github.com/users/kodareef5/gists%7B/gist_id%7D](https://api.github.com/users/kodareef5/gists%7B/gist_id%7D)
- [https://api.github.com/users/kodareef5/repos](https://api.github.com/users/kodareef5/repos)
- [https://avatars.githubusercontent.com/u/261977334?v=4](https://avatars.githubusercontent.com/u/261977334?v=4)
- [https://api.github.com/users/kodareef5/events%7B/privacy%7D](https://api.github.com/users/kodareef5/events%7B/privacy%7D)

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- [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)
- [Client metadata path-traversal](https://junglewise.ai/threats/cve-2021-41131-client-metadata-path-traversal)
- [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)