CVE-2026-75595

CVE-2026-75595 · Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext

This page contains facts from public vulnerability sources. Check the original advisory before updating.

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

CVSS 9.1 · Critical · EPSS 0.3%

Published

2026-08-19T21:00:27.627Z

Updated

2026-08-20T14:06:16.963Z

Stack: system

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