What’s Vulnerable › Vulnerabilities

CVE-2026-100665: Netty 4.2.11 through 4.2.17 QUIC Hostname Verification Bypass

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-26 · updated 2026-10-02
• Weakness: CWE-295

Description

Netty versions from 4.2.11.Final before 4.2.18.Final contain an incomplete hostname verification fix in the QUIC certificate verification path when using a plain X509TrustManager. The BoringSSLCertificateVerifyCallback discards the SSLEngine for plain trust managers, preventing endpoint identification from running even when HTTPS verification is configured. Attackers on the network path can present a certificate chain for the wrong hostname that the plain trust manager accepts, bypassing hostname authentication for QUIC clients.

Affected products

• netty: from 4.2.11.Final before 4.2.18.Final — fixed in 4.2.18.Final

How to fix

Upgrade to a fixed version: netty 4.2.18.Final. Check the vendor advisory for mitigations.

References

• https://github.com/netty/netty/commit/09e72c4fd8007277121ed48db63a124b112b96fe
• https://github.com/netty/netty/commit/994e887ed9
• https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387
• https://www.vulncheck.com/advisories/netty-4.2.11-through-4.2.17-quic-hostname-verification-bypass
• https://github.com/netty/netty/security/advisories/GHSA-mj35-3qqm-q387

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