Arbitrary Filesystem Write Vulnerability in Python3 Package

python3 Updated 02 Oct 2025

Summary

03/06/2025

Disclosed on

N/A

Severity

Yes i

Fix available

Unrated

Severity

Not published

CVSS Score

ALPINE-CVE-2025-4517: Allows arbitrary filesystem writes outside the extraction directory during extraction with filter="data". Affects python3 versions < 3.11.13-r0. Fixed in 3.11.13-r0. How to fix ↓

Free scan

Check if this vulnerability affects your application

Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.

Check my app free

No signup required · Results in about 60 seconds

Upload your dependency manifest or SBOM

Drag & drop your file here or Browse

Java Javascript PHP Python Go Rust Ruby Dart C/C++ Elixir CycloneDX SPDX

Upload a supported dependency manifest or SBOM. No installation or source-code access required.

See supported files and SBOM formats

SBOM sbom.json · bom.json · bom.xml · *.spdx.json · *.cdx.json · *.cdx.xml

Java pom.xml · gradle.lockfile · buildscript-gradle.lockfile

Javascript package-lock.json · yarn.lock · pnpm-lock.yaml

PHP composer.lock

Python poetry.lock · requirements.txt · Pipfile.lock

Go go.mod

Rust Cargo.lock

Ruby Gemfile.lock

Dart pubspec.lock

C/C++ conan.lock

Elixir mix.lock

Enter your work email to receive your report link.

Verify your email to view the full report and start 30 days of continuous monitoring. No credit card required.

Background

Python3 is a widely used programming language known for its simplicity and versatility. It includes a tarfile module that allows users to read and write tar archives. However, this module has a vulnerability that can lead to arbitrary filesystem writes when extracting untrusted tar archives, particularly when using specific extraction filters.

Vulnerability Detail

The vulnerability arises from the tarfile module's handling of extraction filters. When using TarFile.extractall() or TarFile.extract() with the filter parameter set to 'data' or 'tar', it allows arbitrary filesystem writes outside the designated extraction directory. This can lead to unauthorized access or modification of files on the system. The issue is particularly concerning for users relying on the default filter setting, which changed in Python 3.14 from 'no filtering' to 'data'. This change increases the risk for applications that extract untrusted tar archives.

How To Fix

Minimum fixed version

3.11.13-r0

This is the first release that contains the fix.

sudo apk add --upgrade python3

Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →

Workaround

As a temporary workaround, avoid using the filter parameter when extracting tar archives, or ensure that the archives being extracted are from trusted sources. Additionally, consider implementing file system access controls to limit the potential impact of this vulnerability.

Conclusion

The arbitrary filesystem write vulnerability in the Python3 package poses a significant risk when extracting untrusted tar archives. Users are advised to update to the patched versions of the package and implement workarounds until they can ensure their systems are secure.

See every vulnerability recorded for python3 →