Skip to content

Inconsistent Interpretation of HTTP Requests in twisted.web

High severity GitHub Reviewed Published Apr 4, 2022 in twisted/twisted • Updated Jan 27, 2023

Package

pip twisted (pip)

Affected versions

< 22.4.0

Patched versions

22.4.0

Description

The Twisted Web HTTP 1.1 server, located in the twisted.web.http module, parsed several HTTP request constructs more leniently than permitted by RFC 7230:

  1. The Content-Length header value could have a + or - prefix.
  2. Illegal characters were permitted in chunked extensions, such as the LF (\n) character.
  3. Chunk lengths, which are expressed in hexadecimal format, could have a prefix of 0x.
  4. HTTP headers were stripped of all leading and trailing ASCII whitespace, rather than only space and HTAB (\t).

This non-conformant parsing can lead to desync if requests pass through multiple HTTP parsers, potentially resulting in HTTP request smuggling.

Impact

You may be affected if:

  1. You use Twisted Web's HTTP 1.1 server and/or proxy
  2. You also pass requests through a different HTTP server and/or proxy

The specifics of the other HTTP parser matter. The original report notes that some versions of Apache Traffic Server and HAProxy have been vulnerable in the past. HTTP request smuggling may be a serious concern if you use a proxy to perform request validation or access control.

The Twisted Web client is not affected. The HTTP 2.0 server uses a different parser, so it is not affected.

Patches

The issue has been addressed in Twisted 22.4.0rc1 and later.

Workarounds

Other than upgrading Twisted, you could:

  • Ensure any vulnerabilities in upstream proxies have been addressed, such as by upgrading them
  • Filter malformed requests by other means, such as configuration of an upstream proxy

Credits

This issue was initially reported by Zhang Zeyu.

References

@adiroiban adiroiban published to twisted/twisted Apr 4, 2022
Published by the National Vulnerability Database Apr 4, 2022
Published to the GitHub Advisory Database Apr 4, 2022
Reviewed Apr 4, 2022
Last updated Jan 27, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

0.743%
(81st percentile)

Weaknesses

CVE ID

CVE-2022-24801

GHSA ID

GHSA-c2jg-hw38-jrqq

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.