Is CVE-2026-62243 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-62243 being exploited in the wild.

How severe is CVE-2026-62243?

High severity, with a CVSS score of 7.5, published 22 August 2026.

Which products and versions are affected?

Netty-Handler 4.2.0.Final through 4.2.16.Final; 4.1.x through 4.1.136.Final.

Is there a fix for CVE-2026-62243?

A patch was published on 2026-08-22: 4.2.17.Final and 4.1.137.Final Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-62243 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-62243?

Check whether you run Netty-Handler at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-62243: Netty TLS hostname verification bypass in OpenSSL client

CVE-2026-62243 · Severity: high · CVSS 7.5 · Published 2026-08-22

Netty is a Java networking library widely used to build distributed systems and web services. Versions 4.2.0 through 4.2.16 and 4.1.x through 4.1.136 disable TLS hostname verification when running on Java 25+ with the OpenSSL provider. This allows an attacker on the network to intercept connections and present forged certificates for different domains that are silently accepted, enabling account takeover and data interception without detection.

Technologies: Netty-Handler. Vendors: Netty.

Quick answers

Is CVE-2026-62243 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-62243 being exploited in the wild.
How severe is CVE-2026-62243?: High severity, with a CVSS score of 7.5, published 22 August 2026.
Which products and versions are affected?: Netty-Handler 4.2.0.Final through 4.2.16.Final; 4.1.x through 4.1.136.Final.
Is there a fix for CVE-2026-62243?: A patch was published on 2026-08-22: 4.2.17.Final and 4.1.137.Final Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-62243 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-62243?: Check whether you run Netty-Handler at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a TLS hostname verification bypass (CWE-297) affecting Netty's OpenSSL client implementation. When Unsafe-based reflection is unavailable (Java 25+), the hostname verification wrapper defaults to a no-op implementation that returns the plain X509TrustManager without adding verification logic. An attacker positioned as a man-in-the-middle can present a valid certificate issued for a different hostname that will be accepted without validation. The vulnerability requires the use of OpenSSL provider (SslProvider.OPENSSL) with a plain X509TrustManager and Java 25+. Patches are available in versions 4.2.17.Final and 4.1.137.Final.

Affected products

Netty netty-handler 4.2.0.Final through 4.2.16.Final; 4.1.x through 4.1.136.Final

Timeline

2026-08-22: disclosed
2026-08-22: patched: 4.2.17.Final and 4.1.137.Final

References

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