What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-22 · updated 2026-10-14
• Weakness: CWE-297

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.

Affected products

• netty: from 4.2.0.Final before 4.2.16.Final; before 4.1.137.Final — fixed in 4.1.137.Final, 4.2.16.Final

How to fix

Upgrade to a fixed version: netty 4.1.137.Final, 4.2.16.Final. Check the vendor advisory for mitigations.

References

• https://github.com/netty/netty/security/advisories/GHSA-p85m-gvr3-788c
• https://www.vulncheck.com/advisories/netty-through-tls-hostname-verification-bypass

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