Description
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 products
netty: netty
References7
- github.com/netty/netty/security/advisories/GHSA-c4c3-7fpv-j4q5 Vendor Advisory
- github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7d… Patch
- github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139… Patch
- github.com/netty/netty/pull/17213 Issue TrackingPatch
- github.com/netty/netty/pull/17217 Issue TrackingPatch
- github.com/netty/netty/releases/tag/netty-4.1.137.Final Release Notes
- github.com/netty/netty/releases/tag/netty-4.2.17.Final Release Notes
Metrics
- CVSS 3.1
-
9.1
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - CVSS 4.0
-
9.1
CRITICAL
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 25 · as of 10 November 2026
- CWE
- CWE-754
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