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

Quick assessment

Affected
netty netty
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Netty是Netty团队开源的一个高性能网络通信框架。 Netty 4.1.137.Final之前版本和4.2.17.Final之前版本存在异常处理不当漏洞，该漏洞源于SslClientHelloHandler在读取TLS握手标头时检查了错误的偏移量，可能导致未经身份验证的远程攻击者绕过受保护路由的相互TLS要求。

CVSS 9.1 · Critical EPSS 0.32% · P24

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
netty netty < 4.1.137.Final affected
>= 4.2.0.Final, < 4.2.17.Final affected
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I. Basic Information for CVE-2026-75595

Vulnerability Information
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Vulnerability Title
Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对因果或异常条件的不恰当检查
Source: CVE Program / CVE List V5
Vulnerability Title
Netty 异常处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Netty是Netty团队开源的一个高性能网络通信框架。 Netty 4.1.137.Final之前版本和4.2.17.Final之前版本存在异常处理不当漏洞，该漏洞源于SslClientHelloHandler在读取TLS握手标头时检查了错误的偏移量，可能导致未经身份验证的远程攻击者绕过受保护路由的相互TLS要求。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
netty netty < 4.1.137.Final -

II. Public POCs for CVE-2026-75595

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 15956 chars
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III. Intelligence Information for CVE-2026-75595

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Patches & Fixes for CVE-2026-75595 (2)

Vendor Advisories for CVE-2026-75595 (1)

Vendor Pages for CVE-2026-75595 (1)

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-754

V. Comments for CVE-2026-75595

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