CVE-2022-42919

Local privilege escalation vulnerability in Python's multiprocessing library on Linux

• CVSS 7.8
• CWE-502
• Input Validation and Sanitization
• Local

Python 3.9.x before 3.9.16 and 3.10.x before 3.10.9 on Linux allows local privilege escalation in a non-default configuration. The Python multiprocessing library, when used with the forkserver start method on Linux, allows pickles to be deserialized from any user in the same machine local network namespace, which in many system configurations means any user on the same machine. Pickles can execute arbitrary code. Thus, this allows for local user privilege escalation to the user that any forkserver process is running as. Setting multiprocessing.util.abstract_sockets_supported to False is a workaround. The forkserver start method for multiprocessing is not the default start method. This issue is Linux specific because only Linux supports abstract namespace sockets. CPython before 3.9 does not make use of Linux abstract namespace sockets by default. Support for users manually specifying an abstract namespace socket was added as a bugfix in 3.7.8 and 3.8.3, but users would need to make specific uncommon API calls in order to do that in CPython before 3.9.

CVE

CVE-2022-42919

CWE

CWE-502

CVSS base score

7.8

Published

2022-11-07

OWASP

A08 Software and Data Integrity Failures

Orthogonal defect classification

Timing/Serialization

Code defect classification

Serialization Issues

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Local

Impact

Privilege Escalation

Fixed by upgrading

Yes

Solution

Upgrade to Python 3.9.16 or 3.10.9 and set multiprocessing.util.abstract_sockets_supported to False.

import multiprocessing
import pickle

def function():
    # VULNERABLE: This code is susceptible to deserialization
    print("Worker is running")

if __name__ == "__main__":
    multiprocessing.set_start_method('forkserver')

    data = pickle.dumps(function)
    worker = multiprocessing.Process(target=pickle.loads, args=(data,))
    worker.start()
    worker.join()

import multiprocessing

multiprocessing.util.abstract_sockets_supported = False

def function():
    # SECURE: This version prevents deserialization
    print("Worker is running")

if __name__ == "__main__":
    multiprocessing.set_start_method('forkserver')

    worker = multiprocessing.Process(target=function)
    worker.start()
    worker.join()

@misc{vaitp:cve202242919,
  title        = {{Local privilege escalation vulnerability in Python's multiprocessing library on Linux}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2022},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2022-42919},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2022-42919/}}
}