Incomplete path traversal fixes in awslabs/tough before tough-v0.22.0 allow remote authenticated users with delegated signing authority to write files outside intended output directories via absolute target names in copytarget/linktarget, symlinked parent directories in savetarget, or symlinked metadata filenames in SignedRole::write, because write paths trust the joined destination path without post-resolution containment verification.

We recommend you upgrade to tough-v0.22.0 / tuftool-v0.15.0.

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 or directly via email to 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

Summary Missing expiration, hash, and length enforcement in delegated metadata validation in awslabs/tough before tough-v0.22.0 allows remote authenticated users with delegated signing authority to bypass TUF specification integrity checks for delegated targets metadata and poison the local metadata cache, because loaddelegations does not apply the same validation checks as the top-level targets metadata path.

Impact The tough library, prior to 0.22.0, does not properly verify delegated target metadata. It allows someone with write access to the metadata to serve expired or otherwise invalid targets from a TUF repository which tough will then trust rather than reject.

Impacted Versions: tough 0.9.0 through 0.21.x, tuftool through 0.14.x

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-2026-6967 If there are any questions or comments about this advisory, please contact [AWS/Amazon] Security via the vulnerability reporting page or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.

Acknowledgement

Amazon Web Services Labs would like to thank Oleh Konko of 1seal for collaborating on this issue through the coordinated vulnerability disclosure process.

Summary

When updating the root role, a TUF client must establish a trusted line of continuity to the latest set of keys. While sequentially downloading new versions of the root metadata file, tough will not check that the root object version it received was the next sequential version from the previously trusted root metadata.

Impact

The tough client will trust an outdated or rotated root role in the event that an actor with control of the storage medium of a trusted TUF repository inappropriately replaced the contents of one of the root metadata files with an adequately signed previous version. As a result, tough could trust content associated with a previous root role.

Impacted versions: < v0.20.0

Patches

A fix for this issue is available in tough version 0.20.0 and later. Customers are advised to upgrade to version 0.20.0 or later and ensure any forked or derivative code is patched to incorporate the new fixes.

Workarounds

There is no recommended work around. Customers are advised to upgrade to version 0.20.0 or the latest version.

References

If you have any questions or comments about this advisory we ask that you contact AWS/Amazon Security via our vulnerability reporting page [1] or directly via email to aws-security@amazon.com. Please do not create a public GitHub issue.

[1] Vulnerability reporting page: https://aws.amazon.com/security/vulnerability-reporting

Acknowledgement

These issues were identified by the TUF-Conformance project. We would like to thank Google for collaborating on this issue through the coordinated vulnerability disclosure process.