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Client metadata path-traversal

High severity GitHub Reviewed Published Oct 19, 2021 in theupdateframework/python-tuf • Updated Feb 1, 2023

Package

pip tuf (pip)

Affected versions

< 0.19

Patched versions

0.19

Description

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

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

References

@joshuagl joshuagl published to theupdateframework/python-tuf Oct 19, 2021
Reviewed Oct 19, 2021
Published by the National Vulnerability Database Oct 19, 2021
Published to the GitHub Advisory Database Oct 19, 2021
Last updated Feb 1, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

EPSS score

0.141%
(51st percentile)

Weaknesses

CVE ID

CVE-2021-41131

GHSA ID

GHSA-wjw6-2cqr-j4qr

Source code

Credits

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