Netty is an asynchronous, event-driven network application framework

Overview

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.

Affected

• netty < 4.1.137
• netty >= 4.2.0, < 4.2.17

Remediation

Upgrade past the affected range:

• netty 4.2.17

Package advisory (CVE-2026-75595)

Affected packages:

• io.netty:netty-handler >= 4.2.0.Final, <= 4.2.16.Final
• io.netty:netty-handler <= 4.1.136.Final

Patched in:

• io.netty:netty-handler 4.2.17.Final
• io.netty:netty-handler 4.1.137.Final

Source: https://github.com/advisories/GHSA-c4c3-7fpv-j4q5

Vendor advisories

• Red Hat VEX · Important · affected: Red Hat AMQ Clients, Red Hat build of Apache Camel for Spring Boot 4, Red Hat build of Apicurio Registry 3, Red Hat build of Debezium 3, Red Hat Build of Keycloak, Red Hat Ceph Storage 9, … · no fix planned: Red Hat Fuse 7, Red Hat Single Sign-On 7, Red Hat JBoss Enterprise Application Platform 7, Red Hat AMQ Clients, … · updated 2026-09-21 · vex