Vulnerability · Published Aug 22, 2026 · Assigned by VulnCheck

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

High 7.5

In plain English

A high-severity security flaw in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.2%top 95.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	netty	no fix listed	DEBIAN-CVE-2026-62243
Debian:13	netty	no fix listed	DEBIAN-CVE-2026-62243
Debian:14	netty	no fix listed	DEBIAN-CVE-2026-62243
Ubuntu:26.10	netty	no fix listed	UBUNTU-CVE-2026-62243

Affected products (as reported)

Vendor	Product	Versions
netty	netty	4.2.0.Final – before 4.2.16.Final
netty	netty	0 – before 4.1.137.Final

Weakness: CWE-297 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

GitHub Security Advisory (GHSA-p85m-gvr3-788c) vendor-advisory
VulnCheck Advisory: Netty 4.2.0 through 4.2.16 TLS Hostname Verification Bypass third-party-advisory