CVE-2026-6966: awslabs/tough Delegated Roles have a Signature Threshold Bypass
Affects toughSource GCVE Database
Not known to be exploited · CVSS 5.3 Medium : upgrade to 0.22.0 when convenient.
Data as of 27 Oct 2026, 00:07 UTC
- Patch
- Available – fixed in 0.22.0, 0.15.0
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 24 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade tough to 0.22.0; tuftool to 0.15.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| crates.iotough | Affected
| Fixed in
|
| crates.iotuftool | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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](https://aws.amazon.com/security/vulnerability-reporting) or directly via email to [aws-security@amazon.com](mailto:aws-security@amazon.com). 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
References
- github.com/awslabs/tough/security/advisories/GHSA-8m7c-8m39-rv4x (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-6966 (opens in a new tab)
- aws.amazon.com/security/security-bulletins/2026-019-aws (opens in a new tab)
- crates.io/crates/tough/0.22.0 (opens in a new tab)
- crates.io/crates/tuftool/0.15.0 (opens in a new tab)
- github.com/awslabs/tough (opens in a new tab)
- github.com/awslabs/tough/releases/tag/tough-v0.22.0 (opens in a new tab)
- github.com/awslabs/tough/releases/tag/tuftool-v0.15.0 (opens in a new tab)