Summary
uv has differential in tar extraction with PAX headers
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
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.
An object is accessed using a type that is incompatible with its actual type, causing the runtime to interpret memory incorrectly. Typical impact: memory safety violations, unexpected behavior, or code execution.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Versions 0.9.5 and newer of uv address the vulnerability above. Users should upgrade to 0.9.5 or newer.
Frequently Asked Questions
- What is GHSA-W476-P2H3-79G9? GHSA-W476-P2H3-79G9 is a low-severity type confusion vulnerability in uv (pip), affecting versions <= 0.9.4. It is fixed in 0.9.5. An object is accessed using a type that is incompatible with its actual type, causing the runtime to interpret memory incorrectly.
- Which versions of uv are affected by GHSA-W476-P2H3-79G9? uv (pip) versions <= 0.9.4 is affected.
- Is there a fix for GHSA-W476-P2H3-79G9? Yes. GHSA-W476-P2H3-79G9 is fixed in 0.9.5. Upgrade to this version or later.
- Is GHSA-W476-P2H3-79G9 exploitable, and should I be worried? Whether GHSA-W476-P2H3-79G9 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-W476-P2H3-79G9 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-W476-P2H3-79G9? Upgrade
uvto 0.9.5 or later.