Wheel Affected by Arbitrary File Permission Modification via Path Traversal in wheel unpack
Date: 2026-01
Affected: pip/wheel
Attack vector: path-traversal
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-24049
CWE: CWE-22
CVSS: 7.1 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H)

### Summary - **Vulnerability Type:** Path Traversal (CWE-22) leading to Arbitrary File Permission Modification. - **Root Cause Component:** wheel.cli.unpack.unpack function. - **Affected Packages:** 1. wheel (Upstream source) 2. setuptools (Downstream, vendors wheel) - **Severity:** High (Allows modifying system file permissions). ### Details The vulnerability exists in how the unpack function handles file permissions after extraction. The code blindly trusts the filename from the archive header for the chmod operation, even though the extraction process itself might have sanitized the path. ``` # Vulnerable Code Snippet (present in both wheel and setuptools/_vendor/wheel) for zinfo in wf.filelist: wf.extract(zinfo, destination) # (1) Extraction is handled safely by zipfile # (2) VULNERABILITY: # The 'permissions' are applied to a path constructed using the UNSANITIZED 'zinfo.filename'. # If zinfo.filename contains "../", this targets files outside the destination. permissions = zinfo.external_attr >> 16 & 0o777 destination.joinpath(zinfo.filename).chmod(permissions) ``` ### PoC I have confirmed this exploit works against the unpack function imported from setuptools._vendor.wheel.cli.unpack. **Prerequisites:** pip install setuptools **Step 1: Generate the Malicious Wheel (gen_poc.py)** This script creates a wheel that passes internal hash validation but contains a directory traversal payload in the file list.


Mitigations:

Architectural layers (MAESTRO):