GHSA-w476-p2h3-79g9
uv has differential in tar extraction with PAX headers
Blast Radius
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Description
Impact
In versions 0.9.4 and earlier of uv, tar archives containing PAX headers with file size overrides were not handled properly. As a result, an attacker could contrive a source distribution (as a tar archive) that would extract differently when installed via uv versus other Python package installers.
The underlying parsing differential here originates with astral-tokio-tar, which disclosed this vulnerability as CVE-2025-62518.
In practice, the impact of this vulnerability is low: only source distributions can be formatted as tar archives, and source distributions execute arbitrary code at build/installation time by definition. Consequently, a parser differential in tar extraction is strictly less powerful than the capabilities already exposed to an attacker who has the ability to control source distributions.
However, this particular source of malleability in source distributions is unintentional and not operating by design, and therefore we consider it a vulnerability despite its overlap in capabilities with intended behavior.
Patches
Versions 0.9.5 and newer of uv address the vulnerability above. Users should upgrade to 0.9.5 or newer.
Workarounds
Users are advised to upgrade to version 0.9.5 or newer to address this advisory.
Users should experience no breaking changes as a result of the patch above.
References
- See CVE-2025-62518 for the corresponding advisory against astral-tokio-tar
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | uv | all versions | 0.9.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for uv. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update uv to 0.9.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w476-p2h3-79g9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-w476-p2h3-79g9 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-w476-p2h3-79g9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-w476-p2h3-79g9 in your dependencies?
O3 detects GHSA-w476-p2h3-79g9 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.