# CVE-2026-116542: Netty netty-tcnative SNI hostname spoofing

Source: https://junglewise.ai/threats/cve-2026-116542-netty-netty-tcnative-before-2-0-84-final-contains-an-sni  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-26. Updated: 2026-10-26  
License: CC BY 4.0 with a link back

CVE-2026-116542 · Severity: medium · CVSS 5.3 · Published 2026-10-26

Netty's native TLS library (netty-tcnative) has a flaw in how it processes server names from TLS handshakes, allowing attackers to forge or spoof the hostname. This could let attackers bypass certificate validation checks, evade security policies based on domain names, or manipulate access logs by appearing to connect to a different server than they actually target.

Technologies: [Netty-Tcnative](https://junglewise.ai/threats/technologies/tcnative). Vendors: [Netty](https://junglewise.ai/threats/vendors/netty).

## Quick answers

**Is CVE-2026-116542 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-116542 being exploited in the wild.

**How severe is CVE-2026-116542?** Medium severity, with a CVSS score of 5.3, published 26 October 2026.

**Which products and versions are affected?** Netty-Tcnative before 2.0.84.Final; Netty-Tcnative-Boringssl-Static before 2.0.84.Final.

**Is there a fix for CVE-2026-116542?** Yes: fixed in netty-tcnative 2.0.84.Final; netty-tcnative-boringssl-static 2.0.84.Final. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-116542 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-116542?** Check whether you run Netty-Tcnative or Netty-Tcnative-Boringssl-Static 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 netty-tcnative 2.0.84.Final; netty-tcnative-boringssl-static 2.0.84.Final

## Technical details

The vulnerability exists in the JNI NewStringUTF decoding of SNI (Server Name Indication) hostnames within ClientHello messages. Attackers can send overlong UTF-8 encodings (such as 0xC0 0x80 for null bytes) to confuse the hostname parsing, causing certificate selection and access control decisions to operate on a different name than what is logged or validated. The flaw requires network access but no authentication; a fix is available in version 2.0.84.Final.

## Affected products

- Netty netty-tcnative before 2.0.84.Final
- Netty netty-tcnative-boringssl-static before 2.0.84.Final

## Timeline

- 2026-10-26: disclosed

## References

- [https://repo1.maven.org/maven2/io/netty/netty-tcnative/](https://repo1.maven.org/maven2/io/netty/netty-tcnative/)
- [https://repo1.maven.org/maven2/io/netty/netty-tcnative-boringssl-static/](https://repo1.maven.org/maven2/io/netty/netty-tcnative-boringssl-static/)

## Related threats

- [Netty netty-tcnative denial of service in BIO write callback](https://junglewise.ai/threats/cve-2026-116541-netty-netty-tcnative-before-2-0-84-final-contains-a-denial-of)
- [Netty netty-tcnative heap buffer overflow in BIO callback](https://junglewise.ai/threats/cve-2026-116539-netty-netty-tcnative-before-2-0-84-final-contains-a-heap-buffer)