MAVEN · JULY 2026 · EARLY WARNING

Netty WebSockets V07/V08 Handshaker Vulnerability: Early Warning

EARLY WARNING · UNCONFIRMED. This page describes a developing threat that 0Day surfaced from early signals and has not yet independently confirmed. Details may change. Always verify against the primary sources before acting.
GHSA-4MP9-239F-G9HGSeverity: HIGH

An early warning has been issued regarding a potential vulnerability in the Netty WebSockets V07/V08 handshaker that could allow HTTP request smuggling and protocol-confusion attacks.

What happened

Reportedly, an attacker can exploit the lax validation in the Netty WebSockets V07 or V08 handshaker by sending a `Sec-WebSocket-Version: 7` header and omitting the `Connection: Upgrade` and `Upgrade: websocket` headers. This could force a WebSocket upgrade that a proxy might not recognize as an Upgrade request, potentially enabling malicious activities. The affected component is the Netty library (maven). This issue is currently under investigation, and it is recommended to monitor for potential exploitation and apply patches as they become available. For more detailed information, consult the primary sources.

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