Is CVE-2026-116539 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-116539 being exploited in the wild.

How severe is CVE-2026-116539?

Medium severity, with a CVSS score of 5.9, published 26 October 2026.

Which products and versions are affected?

Netty-Tcnative before 2.0.84.Final.

Is there a fix for CVE-2026-116539?

Yes: fixed in 2.0.84.Final. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-116539 attacked?

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

Am I affected by CVE-2026-116539?

Check whether you run Netty-Tcnative 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-2026-116539: Netty netty-tcnative heap buffer overflow in BIO callback

CVE-2026-116539 · Severity: medium · CVSS 5.9 · Published 2026-10-26

Netty's tcnative library, which provides native TLS support for Java applications, contains a heap buffer overflow in its BIO write callback. A remote attacker can exploit this by sending crafted TLS handshake or post-handshake messages, causing the JVM process to crash and resulting in denial of service for applications using this library.

Technologies: Netty-Tcnative. Vendors: Netty.

Quick answers

Is CVE-2026-116539 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-116539 being exploited in the wild.
How severe is CVE-2026-116539?: Medium severity, with a CVSS score of 5.9, published 26 October 2026.
Which products and versions are affected?: Netty-Tcnative before 2.0.84.Final.
Is there a fix for CVE-2026-116539?: Yes: fixed in 2.0.84.Final. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-116539 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-116539?: Check whether you run Netty-Tcnative 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.

How to fix

Fixed in: 2.0.84.Final

Technical details

The vulnerability is a heap buffer overflow in the tcn_write_to_bytebuffer BIO callback caused by improper wrapping of the non-application ring buffer write index. Remote TLS peers can trigger out-of-bounds memcpy operations by sending malicious handshake, renegotiation, or post-handshake messages, leading to JVM process termination.

Affected products

Netty netty-tcnative before 2.0.84.Final

Timeline

2026-10-26: disclosed

References

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