Vulnerability · Published Nov 3, 2026 · Assigned by zdi

CVE-2026-114550libwebsockets MQTT Protocol PUBACK Packet Handling Out-Of-Bounds Write Remote Code Execution Vulnerability

High 8.1

In plain English

A high-severity out-of-bounds write in libwebsockets from libwebsockets. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 58% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.0)8.1High

Exploit odds (30 days)0.8%top 41.9% of all CVEs

Exploited in the wildNo reportsnot in CISA KEV

Attack tooling1Public PoC

Official description

libwebsockets MQTT Protocol PUBACK Packet Handling Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability allows remote attackers to execute arbitrary code on affected installations of libwebsockets. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of PUBACK packets. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-31039.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	libwebsockets	no fix listed	DEBIAN-CVE-2026-114550
Debian:13	libwebsockets	no fix listed	DEBIAN-CVE-2026-114550
Debian:14	libwebsockets	no fix listed	DEBIAN-CVE-2026-114550
Ubuntu:26.10	libwebsockets	no fix listed	UBUNTU-CVE-2026-114550

Affected products (as reported)

Vendor	Product	Versions
libwebsockets	libwebsockets	b4b5aed3903eaff09cd76a410f69bbe5dff66f8e

Weakness: CWE-787 · Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

ZDI-26-792 x_research-advisory
vendor-provided URL vendor-advisory