CVE-2021-41131

Workarounds

None 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.

References

• The issue where this was discovered
• Proof of Concept demonstrating the flaw

For more information

If you have any questions or comments about this advisory:

• Open an issue in python-tuf
• Contact the maintainers by email or Slack

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.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2021-41131 has a CVSS score of 7.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.19.0); upgrading removes the vulnerable code path.

Kodem intelligence

A fix is available in version 0.19 or newer.

1. What is CVE-2021-41131? CVE-2021-41131 is a medium-severity path traversal vulnerability in tuf (pip), affecting versions >= 0, < 0.19.0. It is fixed in 0.19.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2021-41131? CVE-2021-41131 has a CVSS score of 7.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of tuf are affected by CVE-2021-41131? tuf (pip) versions >= 0, < 0.19.0 is affected.
4. Is there a fix for CVE-2021-41131? Yes. CVE-2021-41131 is fixed in 0.19.0. Upgrade to this version or later.
5. Is CVE-2021-41131 exploitable, and should I be worried? Whether CVE-2021-41131 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-41131 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-41131? Upgrade tuf to 0.19.0 or later.

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