# CVE-2026-6966: awslabs/tough Delegated Roles have a Signature Threshold Bypass

Source: https://junglewise.ai/threats/cve-2026-6966-aws-tough-and-tuftool-multiple-vulnerabilities-in-tuf  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-24. Updated: 2026-05-15  
License: CC BY 4.0 with a link back

CVE-2026-6966 · Severity: high · CVSS 5.3 · Published 2026-04-24

Multiple security vulnerabilities have been identified in the tough library and tuftool utility, which are used to manage secure software update repositories. These tools help ensure that software updates are authentic and have not been tampered with. If exploited, these flaws could potentially allow an attacker to compromise the integrity of the update process, leading to the distribution of malicious software to end users.

Technologies: [Amazon AWS](https://junglewise.ai/threats/technologies/aws), [Amazon Tough](https://junglewise.ai/threats/technologies/amazon-tough), [Amazon Tuftool](https://junglewise.ai/threats/technologies/amazon-tuftool), [tough (crates.io)](https://junglewise.ai/threats/technologies/crates-io-tough). Vendors: [Amazon](https://junglewise.ai/threats/vendors/amazon), [AWS](https://junglewise.ai/threats/vendors/aws), [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is CVE-2026-6966 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-6966 being exploited in the wild.

**How severe is CVE-2026-6966?** High severity, with a CVSS score of 5.3, published 24 April 2026.

**Which products and versions are affected?** AWS Tough 0.1.0 - 0.21.x; AWS Tuftool 0.1.0 - 0.14.x; tough (crates.io) SEMVER:introduced=0,fixed=0.22.0; tuftool (crates.io) SEMVER:introduced=0,fixed=0.15.0.

**Is there a fix for CVE-2026-6966?** Yes. tough (crates.io): upgrade to 0.22.0 or later; tuftool (crates.io): upgrade to 0.15.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-6966 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-6966?** Check whether you run Amazon AWS, Amazon Tough, Amazon Tuftool or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- tough (crates.io): upgrade to 0.22.0 or later

  ```sh
  cargo update -p tough
  ```

- tuftool (crates.io): upgrade to 0.15.0 or later

  ```sh
  cargo update -p tuftool
  ```


## Technical details

Multiple vulnerabilities (CVE-2026-6966, CVE-2026-6967, and CVE-2026-6968) exist in the tough Rust library and the tuftool CLI, which implement The Update Framework (TUF). While specific technical root causes for each CVE are not detailed in the advisory, the flaws reside in the components responsible for generating, signing, and managing TUF repositories. An attacker could potentially exploit these issues to bypass security checks inherent in the TUF specification, such as metadata verification or signature validation. Successful exploitation could allow for man-in-the-middle attacks or the serving of malicious repository content. Users are advised to upgrade to tough version 0.22.0 or later and tuftool version 0.15.0 or later.

## Affected products

- AWS tough 0.1.0 - 0.21.x
- AWS tuftool 0.1.0 - 0.14.x

## Identifiers

- CVE-2026-6966
- CVE-2026-6967
- CVE-2026-6968
- GHSA-8m7c-8m39-rv4x

## Timeline

- 2026-04-24: disclosed
- 2026-04-24: advisory
- 2026-04-24: patched

## References

- [https://aws.amazon.com/security/security-bulletins/rss/2026-019-aws/](https://aws.amazon.com/security/security-bulletins/rss/2026-019-aws/)

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