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Incorrect threshold signature computation in TUF

Critical severity GitHub Reviewed Published Aug 20, 2020 in theupdateframework/python-tuf • Updated Sep 7, 2023

Package

pip tuf (pip)

Affected versions

< 0.12.2

Patched versions

0.12.2

Description

Impact

Metadadata signature verification, as used in tuf.client.updater, counted each of multiple signatures with identical authorized keyids separately towards the threshold. Therefore, an attacker with access to a valid signing key could create multiple valid signatures in order to meet the minimum threshold of keys before the metadata was considered valid.

The tuf maintainers would like to thank Erik MacLean of Analog Devices, Inc. for reporting this issue.

Patches

A fix is available in version 0.12.2 or newer.

Workarounds

No workarounds are known for this issue.

References

References

@joshuagl joshuagl published to theupdateframework/python-tuf Aug 20, 2020
Reviewed Aug 21, 2020
Published to the GitHub Advisory Database Aug 21, 2020
Last updated Sep 7, 2023

Severity

Critical

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
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

0.222%
(61st percentile)

Weaknesses

CVE ID

CVE-2020-6174

GHSA ID

GHSA-pwqf-9h7j-7mv8

Source code

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