Umgehung des Extraktionsfilters zur Erstellung von Symlinks zu beliebigen Zielen außerhalb des Extraktionsverzeichnisses

An attacker exploiting CVE-2025-4138 can craft a malicious tar archive designed to extract files outside the intended destination directory. By manipulating symlink targets within the archive, they can overwrite files in sensitive locations, such as system directories or application configuration files. This could lead to arbitrary code execution, data breaches, or complete system compromise. The vulnerability stems from the tarfile module's handling of extraction filters, specifically when filter='data' or filter='tar' is used with untrusted archives. This bypasses intended security checks and allows for traversal outside the designated extraction path.

Systems using Python 3.10.0 through 3.14.0b3 that process untrusted tar archives are at risk. This includes web applications, automation scripts, and any system that relies on the tarfile module to extract archives from external sources. Shared hosting environments where multiple users can upload files are particularly vulnerable.

• python / server:

find / -name '*tar.gz' -o -name '*tar.bz2' -o -name '*tar'

• python / supply-chain:

import os
import tarfile

def check_tarfile_extraction(filepath, destination):
    try:
        with tarfile.open(filepath, 'r') as tar:
            tar.extractall(path=destination, filter='data') # Vulnerable code
        return False # No vulnerability detected
    except Exception as e:
        return True # Vulnerability detected

# Example usage (replace with actual filepaths)
filepath = '/path/to/your/archive.tar.gz'
destination = '/tmp/extraction_test'
if check_tarfile_extraction(filepath, destination):
    print(f"Potential vulnerability detected in {filepath}")
else:
    print(f"No vulnerability detected in {filepath}")

1. 2025-06-03Disclosure

   disclosure

1. Reserviert2025-04-30
2. Veröffentlicht2025-06-03
3. Geändert2026-04-21
4. EPSS aktualisiert2026-03-23

The primary mitigation for CVE-2025-4138 is to upgrade to Python 3.14.0b3 or later, where the default value of the filter parameter has been changed to prevent this behavior. If upgrading is not immediately feasible, avoid using the filter parameter with untrusted tar archives. Alternatively, carefully validate the extraction path and file names within the archive before extracting. Consider using a dedicated tar archive extraction library that implements stricter security checks. For environments where untrusted archives must be processed, implement a sandboxing mechanism to isolate the extraction process.