CVE-2026-6966Published

Signature Threshold Bypass in awslabs/tough Delegated Roles

Collected exploitation and prediction evidence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-6966

Published

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.

Source published: 24 Apr 2026 19:38:24 UTC
Source modified: 20 Oct 2026 18:24:24 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 5.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

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

euvd · EUVD-2026-25627

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Apr 24, 2026, 7:38:24 PM

dateUpdated: Oct 20, 2026, 6:24:24 PM

Source published: Apr 24, 2026, 7:38:24 PM (timezone not stated)
Source modified: Oct 20, 2026, 6:24:24 PM (timezone not stated)
Observed here: 28 Oct 2026 08:46:53 UTC
Source terms: ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD 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

nvd · CVE-2026-6966

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Modified

Weakness classifications: CWE-347

Original publisher date fields

published: 2026-04-24T20:16:28.883

lastModified: 2026-10-26T21:10:00.170

2 source CPE criteria · context only

cpe:2.3:a:amazon:tough:*:*:*:*:*:rust:*:*
cpe:2.3:a:amazon:tuftool:*:*:*:*:*:rust:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 24 Apr 2026 20:16:28 UTC
Source modified: 26 Oct 2026 21:10:00 UTC
Observed here: 27 Oct 2026 15:46:40 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · ff89ba41-3aa1-4d27-914a-91399e9639e5 · Secondary · 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · ff89ba41-3aa1-4d27-914a-91399e9639e5 · Secondary · 5.3 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

osv · GHSA-8m7c-8m39-rv4x

Published

### 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 [[email protected]](mailto:[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

Source published: 5 May 2026 18:46:09 UTC
Source modified: 10 Sep 2026 03:51:04 UTC
Observed here: 24 Oct 2026 13:19:54 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS_V4 · 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

Publisher rating · HIGH