EUVD-2026-25627
GHSA-8m7c-8m39-rv4x
Severity by source
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
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
8DescriptionCVE.org
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.
AnalysisAI
Signature duplication in AWS Tough TUF client prior to v0.22.0 allows authenticated attackers to bypass threshold signature requirements for delegated role metadata by reusing a single valid signature multiple times. The flaw undermines TUF's multi-signature integrity model, enabling acceptance of forged metadata with reduced cryptographic validation. Vendor patch available (tough-v0.22.0, tuftool-v0.15.0). No public exploit code or active exploitation confirmed at time of analysis, but CVSS 7.0 reflects high integrity impact to both vulnerable and downstream systems.
Technical ContextAI
AWS Tough implements The Update Framework (TUF), a security framework for software update systems requiring threshold signatures (N-of-M valid signatures) on repository metadata to prevent tampering. TUF delegated roles allow repository owners to distribute signing authority across multiple keys. CWE-347 (Improper Verification of Cryptographic Signature) manifests here as a signature uniqueness validation failure - the client counts duplicate copies of the same signature toward the threshold requirement rather than enforcing N distinct valid signatures. For example, a 3-of-5 threshold could be satisfied with one valid signature duplicated three times instead of three independent signatures. This affects cpe:2.3:a:aws:tough:*:*:*:*:*:*:*:* (versions prior to 0.22.0) and cpe:2.3:a:aws:tuftool:*:*:*:*:*:*:*:* (versions prior to 0.15.0), the Rust-based TUF client library and tooling published to crates.io and maintained by AWS Labs.
RemediationAI
Upgrade to tough-v0.22.0 or tuftool-v0.15.0 immediately. For Rust projects using Cargo, update Cargo.toml dependencies to tough = "0.22.0" or tuftool = "0.15.0" and run cargo update. Patched releases available at https://github.com/awslabs/tough/releases/tag/tough-v0.22.0, https://github.com/awslabs/tough/releases/tag/tuftool-v0.15.0, and published to crates.io (https://crates.io/crates/tough/0.22.0, https://crates.io/crates/tuftool/0.15.0). No workarounds exist - the vulnerability is in core signature validation logic. If immediate upgrade is not feasible, implement compensating controls by restricting network access to TUF repository clients to trusted networks only, enforcing strict key management for all delegated role signing keys (treat compromise of any single key as critical incident), and implementing out-of-band verification of critical metadata updates until patching is complete. Note that restricting access reduces attack surface but does not eliminate risk from authenticated insiders or compromised credentials. Review recent metadata updates accepted by vulnerable client versions for anomalies such as unexpected role delegations or package additions.
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External POC / Exploit Code
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