GHSA-fcv2-xgw5-pqxf is a medium-severity (CVSS 5.8) Path Traversal vulnerability in github.com/sigstore/sigstore. A fix is available for github.com/sigstore/sigstore — see the affected versions and patch details below.
sigstore legacy TUF client allows for arbitrary file writes with target cache path traversal
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fcv2-xgw5-pqxf.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-fcv2-xgw5-pqxf by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
github.com/sigstore/sigstoreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The legacy TUF client pkg/tuf/client.go, which supports caching target files to disk, constructs a filesystem path by joining a cache base directory with a target name sourced from signed target metadata, but it does not validate that the resulting path stays within the cache base directory.
Note that this should only affect clients that are directly using the TUF client in sigstore/sigstore or are using an older version of Cosign. As this TUF client implementation is deprecated, users should migrate to https://github.com/sigstore/sigstore-go/tree/main/pkg/tuf as soon as possible.
Note that this does not affect users of the public Sigstore deployment, where TUF metadata is validated by a quorum of trusted collaborators.
Impact
A malicious TUF repository can trigger arbitrary file overwriting, limited to the permissions that the calling process has.
Workarounds
Users can disable disk caching for the legacy client by setting SIGSTORE_NO_CACHE=true in the environment, migrate to https://github.com/sigstore/sigstore-go/tree/main/pkg/tuf, or upgrade to the latest sigstore/sigstore release.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sigstore/sigstore | all versions | 1.10.4go get github.com/sigstore/sigstore@v1.10.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sigstore/sigstore, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/sigstore/sigstore to 1.10.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fcv2-xgw5-pqxf is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for GHSA-fcv2-xgw5-pqxf (CC BY 4.0)
Frequently Asked Questions
Is GHSA-fcv2-xgw5-pqxf in your dependencies?
Find it across Go, including transitive dependencies.