CVE-2021-41131: Tuf Client Metadata Path-traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-wjw6-2cqr-j4qr
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CVSS 7.5
CWE-22
Published
Advisory Summary

CVE-2021-41131 is a MODERATE (CVSS 7.5) client metadata path-traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Tuf libraries in the PyPI ecosystem. The issue involves client metadata path-traversal. Remediation is available by upgrading affected packages to version 0.19.0.

CVE-2021-41131 at a Glance

CVE Identifier CVE-2021-41131
GHSA Identifier GHSA-wjw6-2cqr-j4qr
Severity MODERATE
CVSS v3.1 Base Score 7.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Tuf
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-41131

To remediate this vulnerability, upgrade all affected Tuf dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

tuf fixed: 0.19.0 
pip install tuf>=0.19.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show tuf

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-41131, inspect your installed packages using pip:

pip show tuf

Analyze the terminal output to locate any version of Tuf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.19.0), your application is affected.

Note: The pip show tuf command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Tuf, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact 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. ### Patches A fix is available in version 0.19 or newer. ### 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](https://github.com/theupdateframework/python-tuf/issues/1527) - [Proof of Concept demonstrating the flaw](https://github.com/jku/path-traversal-poc) ### For more information If you have any questions or comments about this advisory: * Open an issue in [python-tuf](https://github.com/theupdateframework/python-tuf/issues) * Contact the maintainers by email or Slack

CVE-2021-41131 Affected Tuf Versions

1 component(s)
Fixed Versions:
0.19.0
Product / Package Ecosystem Affected Versions Fixed Version
tuf
pypi/tuf
PyPI
< 0.19.0
0.19.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-wjw6-2cqr-j4qr
NVD — CVE-2021-41131 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-41131
Tuf Source Repository REPOSITORY
https://github.com/theupdateframework/python-tuf/issues/1527
Security Fix Commit FIX COMMIT
https://github.com/theupdateframework/python-tuf/commit/4ad7ae48fda594b640139c3b7eae21ed5155a102
Tuf Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/tuf/PYSEC-2021-376.yaml
Tuf Source Repository REPOSITORY
https://github.com/theupdateframework/python-tuf

Frequently Asked Questions

What is CVE-2021-41131?
CVE-2021-41131 is a security vulnerability in Tuf involving Client metadata path-traversal under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Tuf versions are affected?
Affected versions include releases prior to 0.19.0 across affected packages: tuf.
What version fixes CVE-2021-41131?
Upgrading to 0.19.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tuf affected?
Yes, tuf is affected in releases prior to 0.19.0. Upgrade your dependency to 0.19.0 or later.
What is the CVSS score of CVE-2021-41131?
CVE-2021-41131 has a CVSS v3.1 base score of 7.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N.
What CWE is associated with CVE-2021-41131?
CVE-2021-41131 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check PyPI dependencies for CVE-2021-41131?
Run the dependency tree command: 'pip show tuf'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wjw6-2cqr-j4qr",
  "modified" : "2024-11-18T22:45:45Z",
  "published" : "2021-10-19T20:14:36Z",
  "aliases" : [ "CVE-2021-41131" ],
  "summary" : "Client metadata path-traversal",
  "details" : "### Impact\nIn 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`).\n\nThe impact is mitigated by a few facts:\n* It only affects implementations that allow arbitrary rolename selection for delegated targets metadata\n* 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\n* The written file content is heavily restricted since it needs to be a valid, signed targets file. The file extension is always .json.\n\n### Patches\nA fix is available in version 0.19 or newer.\n\n### Workarounds\nNone 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.\n\n### References\n- [The issue where this was discovered](https://github.com/theupdateframework/python-tuf/issues/1527)\n- [Proof of Concept demonstrating the flaw](https://github.com/jku/path-traversal-poc)\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [python-tuf](https://github.com/theupdateframework/python-tuf/issues)\n* Contact the maintainers by email or Slack\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "tuf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.19.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-wjw6-2cqr-j4qr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-41131"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/issues/1527"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/theupdateframework/python-tuf/commit/4ad7ae48fda594b640139c3b7eae21ed5155a102"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/tuf/PYSEC-2021-376.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/theupdateframework/python-tuf"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-10-19T16:09:34Z",
    "nvd_published_at" : "2021-10-19T18:15:00Z"
  }
}