# CVE-2026-116541: Netty netty-tcnative denial of service in BIO write callback

Source: https://junglewise.ai/threats/cve-2026-116541-netty-netty-tcnative-before-2-0-84-final-contains-a-denial-of  
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-2026-116541 · Severity: medium · CVSS 5.9 · Published 2026-10-26

Netty's TLS library contains a flaw in how it reports bytes consumed by the BIO write callback, allowing remote TLS 1.3 peers to send specially crafted post-handshake records. This can cause connections to fail, truncate message flights, or crash the Java process hosting the application, leading to service disruption.

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

## Quick answers

**Is CVE-2026-116541 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-116541 being exploited in the wild.

**How severe is CVE-2026-116541?** 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; Netty-Tcnative-Boringssl-Static before 2.0.84.Final.

**Is there a fix for CVE-2026-116541?** 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-2026-116541 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-116541?** 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 2.0.84.Final

## Technical details

The tcn_write_to_bytebuffer BIO write callback in netty-tcnative incorrectly overreports the number of bytes consumed, causing buffer management errors when handling TLS 1.3 post-handshake messages (NewSessionTicket, KeyUpdate). A remote peer can exploit this over the network to trigger denial of service without authentication by sending malformed or oversized post-handshake records.

## 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 SNI hostname spoofing](https://junglewise.ai/threats/cve-2026-116542-netty-netty-tcnative-before-2-0-84-final-contains-an-sni)
- [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)