Connect your agent
AdvisoriesCriticalCheck your lockfilePluginHow it worksPricing Connect your agent

Advisory record · GHSA-4mp9-239f-g9hg

Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation

CVSS 6.3 MediumEPSS 0.0044 · 38th percentile

Published by the GitHub Advisory Database at 22 Jul 2026, 21:48 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
io.netty:netty-codec-httpMaven>=4.2.0.Final, <4.2.16.Final || <4.1.136.Final4.2.16.Final, 4.1.136.Final
Identifiers
GHSA-4mp9-239f-g9hg · CVE-2026-59898
Weakness (CWE)
CWE-444
Tags
Published
22 Jul 2026
Updated
10 Sept 2026

Machine-written summary

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

Netty's netty-codec-http package, versions 4.2.0.Final before 4.2.16.Final and before 4.1.136.Final, has a WebSocket V07/V08 handshaker that skips checking the Connection and Upgrade headers. A remote attacker can send a request with a WebSocket version header and no upgrade headers, which can complete a protocol switch that a proxy does not treat as an upgrade, enabling HTTP request smuggling and protocol-confusion attacks. Upgrade to netty-codec-http 4.2.16.Final or 4.1.136.Final.

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
6.3 Medium 4.0 CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0044, the 38th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:16 UTC First seen by agentprime
  2. 31 Oct 2026, 14:16 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.