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CVE-2026-62243— Netty 4.2.0 through 4.2.16 TLS Hostname Verification Bypass

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（io.netty:netty-handler）4.2.0.Final 至 4.2.16.Final 版本，以及 4.1.136.Final 及更早版本，在使用普通的（非扩展的）X509TrustManager 且无法使用基于 Unsafe 的信任管理器包装（Java 25+）时，会在 SslProvider.OPENSSL 客户端路径中禁用 TLS 主机名验证。在此配置下，OpenSSL 客户端不会执行主机名验证，使得中间人攻击者可以提供一个为其他主机名签发的证书，且该证书会被接受而未经过验证。该问题已

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1557.002 · ARP Cache Poisoning

Affected Version Matrix 4

VendorProduct Version RangeStatus
netty netty 4.2.0.Final< 4.2.16.Final affected
4.2.16.Final unaffected
< 4.1.137.Final affected
4.1.137.Final unaffected
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I. Basic Information for CVE-2026-62243

Vulnerability Information
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Vulnerability Title
Netty 4.2.0 through 4.2.16 TLS Hostname Verification Bypass
Source: CVE Program / CVE List V5
Vulnerability Description
Netty (io.netty:netty-handler) versions from 4.2.0.Final through 4.2.16.Final and versions through 4.1.136.Final disable TLS hostname verification on the SslProvider.OPENSSL client path when a plain (non-extended) X509TrustManager is used and Unsafe-based trust-manager wrapping is unavailable (Java 25+). In this configuration the OpenSSL client does not perform hostname verification, allowing a man-in-the-middle attacker to present a certificate issued for a different hostname that is accepted without validation. Fixed in 4.2.17.Final and 4.1.137.Final.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对宿主不匹配的证书验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
netty netty 4.2.0.Final ~ 4.2.16.Final -
netty netty 0 ~ 4.1.137.Final -

II. Public POCs for CVE-2026-62243

# POC Description Source Link Shenlong Link
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Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
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claude_code · 16267 chars
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III. Intelligence Information for CVE-2026-62243

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Vendor Advisories for CVE-2026-62243 (2)

IV. Related Vulnerabilities

Same product: netty
Same vendor: netty
Same weakness: CWE-297

V. Comments for CVE-2026-62243

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