Vulnerabilities CVE-2026-59898

CVE-2026-59898

Medium

Open

TLP:CLEAR

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

NVD CVE.org

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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.

Details

CVSS Score: 6.3
EPSS Score ⓘ: 0.25%

16.4th percentile
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
Confidence: 90%
Published: Jul 29, 2026
Last Modified: Jul 30, 2026

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