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

HIGH 7.5CVE-2026-59898 · GHSA-4mp9-239f-g9hg · Published 29/07/2026 · updated 06/08/2026

Package	Affected versions	Patched versions
io.netty:netty-codec-http Maven	`≥ 4.2.0.Final, < 4.2.16.Final< 4.1.136.Final`	`4.2.16.Final4.1.136.Final`
netty netty	`≥ 4.2.0, < 4.2.16< 4.1.136`	`4.2.164.1.136`

Description

Summary

An attacker can force WebSocket upgrade via the lax V07 (or V08) handshaker by sending Sec-WebSocket-Version: 7 and omitting Connection: Upgrade / Upgrade: websocket headers, completing a protocol switch that a proxy would not recognize as an Upgrade request and enabling HTTP request smuggling / protocol-confusion attacks.

NVD description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, ab attacker can force WebSocket upgrade via the lax V07 (or V08) handshaker by sending `Sec-WebSocket-Version: 7` and omitting `Connection: Upgrade` / `Upgrade: websocket` headers, completing a protocol switch that a proxy would not recognize as an Upgrade request and enabling HTTP request smuggling / protocol-confusion attacks. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

References

netty/netty security advisory · WEB
netty/netty · PACKAGE
netty/netty release netty-4.1.136.Final · WEB
netty/netty release netty-4.2.16.Final · WEB

Running one of these products? Scan your site to see whether it exposes a vulnerable version.

Scan my site free