# PYSEC-2019-68 - In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request…

Source: https://junglewise.ai/threats/pysec-2019-68-in-waitress-through-version-1-4-0-if-a-proxy-server-is-4705649e  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2019-12-26  
License: CC BY 4.0 with a link back

Severity: info · Published 2019-12-26

In Waitress through version 1.4.0, if a proxy server is used in front of waitress, an invalid request may be sent by an attacker that bypasses the front-end and is parsed differently by waitress leading to a potential for HTTP request smuggling. Specially crafted requests containing special whitespace characters in the Transfer-Encoding header would get parsed by Waitress as being a chunked request, but a front-end server would use the Content-Length instead as the Transfer-Encoding header is considered invalid due to containing invalid characters. If a front-end server does HTTP pipelining to a backend Waitress server this could lead to HTTP request splitting which may lead to potential cache poisoning or unexpected information disclosure. This issue is fixed in Waitress 1.4.1 through more strict HTTP field validation.

Technologies: [waitress (PyPI)](https://junglewise.ai/threats/technologies/waitress). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Informational severity, published 26 December 2019.

**Which products and versions are affected?** waitress (PyPI) GIT:introduced=0,fixed=11d9e138125ad46e951027184b13242a3c1de017|ECOSYSTEM:introduced=0,fixed=1.4.1.

**Is there a fix for This vulnerability?** Yes. waitress (PyPI): upgrade to 1.4.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected?** Check whether you run waitress (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- waitress (PyPI): upgrade to 1.4.1 or later

  ```sh
  pip install "waitress>=1.4.1"
  ```


## Affected products

- waitress (PyPI) GIT:introduced=0,fixed=11d9e138125ad46e951027184b13242a3c1de017|ECOSYSTEM:introduced=0,fixed=1.4.1

## Related threats

- [Waitress denial of service via unclean socket handling](https://junglewise.ai/threats/cve-2024-49769-waitress-denial-of-service-via-unclean-socket-handling)
- [Waitress has request processing race condition in HTTP pipelining with invalid first request](https://junglewise.ai/threats/cve-2024-49768-waitress-has-request-processing-race-condition-in-http-pipelining)
- [Uncaught Exception (due to a data race) leads to process termination in Waitress](https://junglewise.ai/threats/cve-2022-31015-uncaught-exception-due-to-a-data-race-leads-to-process)
- [HTTP Request Smuggling in waitress](https://junglewise.ai/threats/cve-2022-24761-http-request-smuggling-in-waitress)
- [Catastrophic backtracking in regex allows Denial of Service in Waitress](https://junglewise.ai/threats/cve-2020-5236-catastrophic-backtracking-in-regex-allows-denial-of-service-in)