CVE-2022-24761: Waitress is a Web Server Gateway Interface server for Python 2 and 3. When using Waitress versions 2.1.0 and prior behind a proxy that does not proper...

Description

Waitress is a Web Server Gateway Interface server for Python 2 and 3. When using Waitress versions 2.1.0 and prior behind a proxy that does not properly validate the incoming HTTP request matches the RFC7230 standard, Waitress and the frontend proxy may disagree on where one request starts and where it ends. This would allow requests to be smuggled via the front-end proxy to waitress and later behavior. There are two classes of vulnerability that may lead to request smuggling that are addressed by this advisory: The use of Python's `int()` to parse strings into integers, leading to `+10` to be parsed as `10`, or `0x01` to be parsed as `1`, where as the standard specifies that the string should contain only digits or hex digits; and Waitress does not support chunk extensions, however it was discarding them without validating that they did not contain illegal characters. This vulnerability has been patched in Waitress 2.1.1. A workaround is available. When deploying a proxy in front of waitress, turning on any and all functionality to make sure that the request matches the RFC7230 standard. Certain proxy servers may not have this functionality though and users are encouraged to upgrade to the latest version of waitress instead.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS Probability

1.79%

75.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Agendaless	Waitress	< 2.1.1
Debian	Debian Linux	9.0

References

https://github.com/Pylons/waitress/commit/9e0b8c801e4d505c2ffc91b891af4ba48af715e0Patch, Release Notes, Third Party Advisory
https://github.com/Pylons/waitress/releases/tag/v2.1.1Release Notes, Third Party Advisory
https://github.com/Pylons/waitress/security/advisories/GHSA-4f7p-27jc-3c36Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/05/msg00011.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5138Third Party Advisory
https://github.com/Pylons/waitress/commit/9e0b8c801e4d505c2ffc91b891af4ba48af715e0Patch, Release Notes, Third Party Advisory
https://github.com/Pylons/waitress/releases/tag/v2.1.1Release Notes, Third Party Advisory
https://github.com/Pylons/waitress/security/advisories/GHSA-4f7p-27jc-3c36Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/05/msg00011.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5138Third Party Advisory

Timeline

Published: Mar 17, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-24761?

Waitress is a Web Server Gateway Interface server for Python 2 and 3. When using Waitress versions 2.1.0 and prior behind a proxy that does not properly validate the incoming HTTP request matches the RFC7230 standard, Waitress and the frontend proxy may disagree on where one request starts and where it ends. This would allow requests to be smuggled via the front-end proxy to waitress and later behavior. There are two classes of vulnerability that may lead to request smuggling that are addressed by this advisory: The use of Python's `int()` to parse strings into integers, leading to `+10` to be parsed as `10`, or `0x01` to be parsed as `1`, where as the standard specifies that the string should contain only digits or hex digits; and Waitress does not support chunk extensions, however it was discarding them without validating that they did not contain illegal characters. This vulnerability has been patched in Waitress 2.1.1. A workaround is available. When deploying a proxy in front of waitress, turning on any and all functionality to make sure that the request matches the RFC7230 standard. Certain proxy servers may not have this functionality though and users are encouraged to upgrade to the latest version of waitress instead.

How severe is CVE-2022-24761?

CVE-2022-24761 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.79% probability of exploitation in the next 30 days.

How do I fix CVE-2022-24761?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.