---
title: "CVE-2024-49768: Waitress has request processing race condition in HTTP pipelining with invalid first request"
url: https://erroneo.us/security/cve/CVE-2024-49768/
description: "CVE-2024-49768 (waitress (PyPI)): Waitress is a Web Server Gateway Interface server for Python 2 and 3. A remote client may send a request that is exactly…"
type: vulnerability-record
section: "Security Digest"
date_published: 2024-10-29
date_modified: 2025-01-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2024-49768"
kev: false
cvss: 9.3
epss: 0.00486
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2024-49768: Waitress has request processing race condition in HTTP pipelining with invalid first request

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5% , percentile 41: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 41% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes waitress (PyPI) >= 2.0.0, < 3.0.1, fixed in 3.0.1 . Check your lockfile, including transitive dependencies.

## What it is

Waitress is a Web Server Gateway Interface server for Python 2 and 3. A remote client may send a request that is exactly recvbytes (defaults to 8192) long, followed by a secondary request using HTTP pipelining. When request lookahead is disabled (default) we won't read any more requests, and when the first request fails due to a parsing error, we simply close the connection. However when request lookahead is enabled, it is possible to process and receive the first request, start sending the error message back to the client while we read the next request and queue it. This will allow the secondary request to be serviced by the worker thread while the connection should be closed. Waitress 3.0.1 fixes the race condition. As a workaround, disable channelrequestlookahead, this is set to 0 by default disabling this feature.

## Affected packages

- PyPI `waitress` >= 2.0.0, < 3.0.1 → fixed: 3.0.1

## Affected products (CVE record)

- Pylons waitress: >= 2.0.0, < 3.0.1

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.49% probability of exploitation activity in the next 30 days; percentile 41.

## Sources

- [GitHub Advisory GHSA-9298-4cf8-g4wj](https://github.com/advisories/GHSA-9298-4cf8-g4wj)
- [CVE.org record CVE-2024-49768](https://www.cve.org/CVERecord?id=CVE-2024-49768)
- [NVD entry CVE-2024-49768](https://nvd.nist.gov/vuln/detail/CVE-2024-49768)
- [github.com](https://github.com/Pylons/waitress/security/advisories/GHSA-9298-4cf8-g4wj)
- [github.com](https://github.com/Pylons/waitress/commit/e4359018537af376cf24bd13616d861e2fb76f65)
- [github.com](https://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2024-210.yaml)

---
Source page: https://erroneo.us/security/cve/CVE-2024-49768/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt