CVE-2026-59898 MEDIUM

CVE-2026-59898: Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation

Vendor Netty
Product netty
Weakness CWE-444
Published July 29, 2026
Last update July 30, 2026
View on NVD All CVEs

CVSS base score

6.3/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

July 29, 2026 CVE published
July 30, 2026 Record updated