CVE-2011-4213

Google App Engine Python SDK < 1.5.4 sandbox os module bypass

• CVSS 7.2
• CWE-264: Permissions, Privileges, and Access Controls
• Input Validation and Sanitization
• Local

The sandbox environment in the Google App Engine Python SDK before 1.5.4 does not properly prevent use of the os module, which allows local users to bypass intended access restrictions and execute arbitrary commands via a file_blob_storage.os reference within the code parameter to _ah/admin/interactive/execute, a different vulnerability than CVE-2011-1364.

CVE

CVE-2011-4213

CWE

CWE-264: Permissions, Privileges, and Access Controls

CVSS base score

7.2

Published

2011-10-30

OWASP

A10 Server Side Request Forgery (SSRF)

Orthogonal defect classification

Function

Code defect classification

Incorrect Functionality

Category

Input Validation and Sanitization

Subcategory

Insecure Direct Object References (IDOR)

Accessibility scope

Local

Impact

Arbitrary Code Execution

Fixed by upgrading

Yes

Solution

Update Google App Engine Python SDK to version 1.5.4 or higher.

import os

def function(code):
    """Vulnerable function that demonstrates the security issue."""
    exec(code)

user_input = "os.system('echo Vulnerable!')"
function(user_input)

import os

BLACKLIST = ['os.system', 'exec', 'eval', 'subprocess', 'open', '__import__']

def function(code):
    """Secure function that fixes the vulnerability."""
    # SECURE: This version prevents command injection
    for item in BLACKLIST:
        if item in code:
            raise ValueError(f"Use of {item} is not allowed.")
    
    exec(code)

user_input = "os.system('echo Vulnerable!')"

try:
    function(user_input)
except ValueError as e:
    print(f"Error: {e}")

@misc{vaitp:cve20114213,
  title        = {{Google App Engine Python SDK < 1.5.4 sandbox os module bypass}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2011},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2011-4213},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2011-4213/}}
}