Vulnerability in buildkit project (sigstore package related to its legacy TUF client)

[ankitdn]

Contributing guidelines and issue reporting guide

• I've read the contributing guidelines and wholeheartedly agree. I've also read the issue reporting guide.

Well-formed report checklist

• I have found a bug that the documentation does not mention anything about my problem
• I have found a bug that there are no open or closed issues that are related to my problem
• I have provided version/information about my environment and done my best to provide a reproducer

Description of bug

While working on buildkit project, I identified a security vulnerability in the sigstore package related to its legacy TUF client implementation. The issue exists in the file caching mechanism used to store TUF target files on disk. The vulnerability occurs because the legacy TUF client constructs file paths by combining a cache base directory with a target name obtained from signed metadata without validating whether the final path stays within the intended cache directory.

CVE Link
CVE Report

[tonistiigi]

If you have an example of how this vulnerability affects the verifier in https://github.com/moby/policy-helpers, then please open a new issue in that repository with an example.