CVE-2026-59898

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

State: Published
Severity: 6.3 Medium
Published: Jul 29, 2026
Updated: Jul 30, 2026
Reserved: Jul 7, 2026

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.

Scores

CVSS	Score	Vector	Source
4.0	6.3 Medium	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	GitHub_M

Weaknesses

CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

Affected Products

Product	Versions
nettynetty	>=4.2.0.Final, < 4.2.16.FinalAffected < 4.1.136.FinalAffected

References

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