GHSA-8m7c-8m39-rv4x
MEDIUMGHSA-8m7c-8m39-rv4x is a medium-severity (CVSS 5.3) vulnerability in tough. O3 Security confirms whether GHSA-8m7c-8m39-rv4x is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
awslabs/tough Delegated Roles have a Signature Threshold Bypass
Real-World Exposure
tough🦀tuftoolReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
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
- CVE-2026-6966
If there are any questions or comments about this advisory, please contact [AWS/Amazon] Security via the vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
Acknowledgement
Amazon Web Services Labs would like to thank Emily Albini of Oxide Computer and Oleh Konko of 1seal for collaborating on this issue through the coordinated vulnerability disclosure process
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | tough | all versions | 0.22.0 |
| 🦀crates.io | tuftool | all versions | 0.15.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tough. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update tough to 0.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8m7c-8m39-rv4x is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-8m7c-8m39-rv4x is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-8m7c-8m39-rv4x. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-8m7c-8m39-rv4x in your dependencies?
O3 detects GHSA-8m7c-8m39-rv4x across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.