Python CPython up to 3.14.0b1 TarFile.extractall/TarFile.extract path traversal

Summaryinfo

A vulnerability, which was classified as critical, has been found in Python CPython up to 3.14.0b1. Affected is the function TarFile.extractall/TarFile.extract. This manipulation causes path traversal. The identification of this vulnerability is CVE-2025-4138. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Python CPython up to 3.14.0b1. Affected by this vulnerability is the function TarFile.extractall/TarFile.extract. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality. The summary by CVE is:

Allows the extraction filter to be ignored, allowing symlink targets to point outside the destination directory, and the modification of some file metadata. You are affected by this vulnerability if using the tarfile module to extract untrusted tar archives using TarFile.extractall() or TarFile.extract() using the filter= parameter with a value of "data" or "tar". See the tarfile extraction filters documentation https://docs.python.org/3/library/tarfile.html#tarfile-extraction-filter  for more information. Only Python versions 3.12 or later are affected by these vulnerabilities, earlier versions don't include the extraction filter feature. Note that for Python 3.14 or later the default value of filter= changed from "no filtering" to `"data", so if you are relying on this new default behavior then your usage is also affected. Note that none of these vulnerabilities significantly affect the installation of source distributions which are tar archives as source distributions already allow arbitrary code execution during the build process. However when evaluating source distributions it's important to avoid installing source distributions with suspicious links.

The advisory is shared at github.com. This vulnerability is known as CVE-2025-4138 since 04/30/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1006 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 240322 (Amazon Linux 2023 : python3.12, python3.12-devel, python3.12-idle (ALAS2023-2025-1044)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.14.0b2 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (240322), EUVD (EUVD-2025-16724) and CERT Bund (WID-SEC-2025-1850). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Xerox FreeFlow Print Server

Productinfo

Type

• Programming Language Software

Vendor

• Python

Name

• CPython

Version

• 3.14.0b1

License

• open-source

Website

• Product: https://github.com/python/cpython/

CPE 2.3info

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CPE 2.2info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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