CVE-2022-24801

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.

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.

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.

CVE-2022-24801 has a CVSS score of 8.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (22.4.0); upgrading removes the vulnerable code path.

Kodem intelligence

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

1. What is CVE-2022-24801? CVE-2022-24801 is a critical-severity security vulnerability in twisted (pip), affecting versions < 22.4.0. It is fixed in 22.4.0.
2. How severe is CVE-2022-24801? CVE-2022-24801 has a CVSS score of 8.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of twisted are affected by CVE-2022-24801? twisted (pip) versions < 22.4.0 is affected.
4. Is there a fix for CVE-2022-24801? Yes. CVE-2022-24801 is fixed in 22.4.0. Upgrade to this version or later.
5. Is CVE-2022-24801 exploitable, and should I be worried? Whether CVE-2022-24801 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2022-24801 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2022-24801? Upgrade twisted to 22.4.0 or later.

Other vulnerabilities in twisted