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Advisory record · GHSA-xrr9-rh8p-433v

Request smuggling is possible when both chunked TE and content length specified

CVSS 5.4 MediumEPSS 0.0076 · 55th percentile

Published by the GitHub Advisory Database at 27 Jan 2020, 19:28 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
io.ktor:ktor-client-cioMaven<1.3.01.3.0
io.ktor:ktor-server-cioMaven<1.3.01.3.0
Identifiers
GHSA-xrr9-rh8p-433v · CVE-2020-5207
Weakness (CWE)
CWE-444
Tags
Published
27 Jan 2020
Updated
8 Jul 2026

Machine-written summary

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

Ktor's ktor-client-cio and ktor-server-cio (Maven) versions before 1.3.0 are vulnerable to request smuggling when running behind a proxy that mishandles Content-Length and Transfer-Encoding headers or treats a bare newline as a header separator. An attacker able to send requests through such a proxy could smuggle requests past it. Upgrade to version 1.3.0 or later. The source gives no workaround other than changing to a different proxy.

Written 2 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
5.4 Medium 3.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0076, the 55th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:20 UTC First seen by agentprime
  2. 31 Oct 2026, 14:20 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.