# CVE-2026-114550: libwebsockets MQTT PUBACK packet out-of-bounds write

Source: https://junglewise.ai/threats/cve-2026-114550-libwebsockets-mqtt-protocol-puback-packet-handling-out-of-bounds  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-114550 · Severity: high · CVSS 8.1 · Published 2026-11-04

libwebsockets is a library used in network applications to implement the WebSocket and MQTT protocols. A flaw in how it processes MQTT PUBACK (acknowledgment) packets allows a remote attacker to write data beyond allocated memory boundaries, enabling arbitrary code execution without requiring authentication or user interaction.

## Quick answers

**Is CVE-2026-114550 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-114550 being exploited in the wild.

**How severe is CVE-2026-114550?** High severity, with a CVSS score of 8.1, published 4 November 2026.

**Which products and versions are affected?** libwebsockets.

**Is there a fix for CVE-2026-114550?** Yes: fixed in libwebsockets (commit c9e8e1834d7f13038c82963086b90e2ee9c5b44c or later). Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-114550 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-114550?** Check whether you run Libwebsockets. 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 libwebsockets (commit c9e8e1834d7f13038c82963086b90e2ee9c5b44c or later)

## Technical details

An out-of-bounds write vulnerability exists in the MQTT protocol parser's handling of PUBACK packets due to insufficient validation of packet data. The vulnerability resides in lib/roles/mqtt/mqtt.c and can be triggered remotely over the network by sending a malformed PUBACK packet. An unauthenticated attacker can exploit this to achieve code execution in the context of the affected process.

## Affected products

- libwebsockets

## Timeline

- 2026-07-16: disclosed: Vulnerability reported to vendor
- 2026-10-26: advisory: Coordinated public release of advisory ZDI-26-792
- 2026-10-26: patched: Fix available via GitHub commit

## References

- [https://github.com/warmcat/libwebsockets/commit/c9e8e1834d7f13038c82963086b90e2ee9c5b44c](https://github.com/warmcat/libwebsockets/commit/c9e8e1834d7f13038c82963086b90e2ee9c5b44c)
- [https://www.zerodayinitiative.com/advisories/ZDI-26-792/](https://www.zerodayinitiative.com/advisories/ZDI-26-792/)