Medium severity · published Apr 24, 2026
CVE-2026-6966
Signature Threshold Bypass in awslabs/tough Delegated Roles
6.5
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 21% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
tough · AWS
0.9.0 through 0.21 · source: vendor, NVD
TU
tuftool · AWS
through 0.14 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6966
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6966
Vendor Advisory
https://aws.amazon.com/security/security-bulletins/2026-019-aws/
Product
https://crates.io/crates/tough/0.22.0
Product
https://crates.io/crates/tuftool/0.15.0
Release Notes
https://github.com/awslabs/tough/releases/tag/tough-v0.22.0
Release Notes
https://github.com/awslabs/tough/releases/tag/tuftool-v0.15.0
Vendor Advisory
https://github.com/awslabs/tough/security/advisories/GHSA-8m7c-8m39-rv4x
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6.5
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