awslabs/tough Delegated Roles have a Signature Threshold Bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.0 · CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N · score source

EPSS

• CVE-2026-6966: 0.28% estimated exploitation activity in the next 30 days; percentile 20.86 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 signature, causing the client to accept forged delegated role metadata. Impact The tough library, prior to 0.22.0, does not properly verify the uniqueness of keys in the signatures provided to meet the threshold of cryptographic signatures in delegated targets. It allows actors with access to a valid signing key to create multiple valid signatures in order to circumvent TUF requiring a minimum threshold of unique keys before the metadata is considered valid. Patches This issue has been addressed in tough version 0.22.0 and tuftool version 0.15.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes. Workarounds No workarounds to this issue are known. References…

Published by the source

5 May 2026, 18:46 UTC

Last modified by the source

5 May 2026, 18:46 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8m7c-8m39-rv4x

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# Patch Next advisory brief: CVE-2026-6966

Advisory: awslabs/tough Delegated Roles have a Signature Threshold Bypass
IDs: CVE-2026-6966, GHSA-8m7c-8m39-rv4x
Record: https://patchnext.com/advisories/cve-2026-6966 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tough 0.22.0; tuftool 0.15.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io tough: affected < 0.22.0; fixed in 0.22.0
- crates.io tuftool: affected < 0.15.0; fixed in 0.15.0

## Suggested inspection (read-only)
- crates.io tough: check the installed version with your package manager.
- crates.io tuftool: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tough, tuftool.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8m7c-8m39-rv4x (GitHub-reviewed advisory GHSA-8m7c-8m39-rv4x lists affected ranges: crates.io tough >=0 =0 <0.15.0)

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