---
id: CVE-2026-6966
title: Signature Threshold Bypass in awslabs/tough Delegated Roles
summary: >-
  Improper verification of cryptographic signature uniqueness in delegated role
  validation in awslabs/tough before tough-v0.22.0 allows remote authenticated
  users to bypass the TUF signature threshold requirement by duplicating a valid
  sig…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N'
cvssSource: cna
cwe:
  - CWE-347
vendor: AWS
product: tough
affected:
  - tough >= 0.9.0 <= 0.21
  - tuftool <= 0.14
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-04-24T20:15:12.033311Z'
published: '2026-04-24'
updated: '2026-10-20'
sourceUpdated: '2026-10-20T18:24:24.155Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-6966'
references:
  - url: 'https://aws.amazon.com/security/security-bulletins/2026-019-aws/'
  - url: 'https://github.com/awslabs/tough/releases/tag/tough-v0.22.0'
  - url: 'https://github.com/awslabs/tough/releases/tag/tuftool-v0.15.0'
  - url: 'https://crates.io/crates/tough/0.22.0'
  - url: 'https://crates.io/crates/tuftool/0.15.0'
  - url: 'https://github.com/awslabs/tough/security/advisories/GHSA-8m7c-8m39-rv4x'
tags:
  - cve.org
epss: 0.0037
epssPercentile: 0.29461
ingestedAt: '2026-10-20T19:16:14.551Z'
---

## Overview

Improper verification of cryptographic signature uniqueness in delegated role validation in awslabs/tough before tough-v0.22.0 allows remote authenticated users to bypass the TUF signature threshold requirement by duplicating a valid signature, causing the client to accept forged delegated role metadata.



We recommend you upgrade to tough-v0.22.0 / tuftool-v0.15.0.

## Affected

- `tough >= 0.9.0 <= 0.21`
- `tuftool <= 0.14`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.