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Advisory record · GHSA-pg36-wpm5-g57p

HTTP Request Smuggling: LF vs CRLF handling in Waitress

CVSS 7.1 HighEPSS 0.025 · 85th percentile

Published by the GitHub Advisory Database at 20 Dec 2019, 23:03 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
waitressPyPI<1.4.01.4.0
Identifiers
GHSA-pg36-wpm5-g57p · CVE-2019-16785 · PYSEC-2019-136
Weakness (CWE)
CWE-444
Tags
Published
20 Dec 2019
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Waitress versions before 1.4.0 can parse HTTP requests differently from a front-end proxy when a bare LF is used as a line terminator, which can allow HTTP request smuggling. An attacker able to send crafted requests through a front-end server could smuggle a second request to Waitress. Upgrade to Waitress 1.4.0, which requires CRLF line terminators and returns 400 Bad Request for bare CR or LF.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.1 High 3.1 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.025, the 85th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:37 UTC First seen by agentprime
  2. 31 Oct 2026, 14:37 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.