CVE-2026-59898: Netty

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Netty Netty: before 4.1.136 (fixed in 4.1.136); from 4.2.0, before 4.2.16 (fixed in 4.2.16)

Published 2026-07-29. Last modified 2026-08-06.