Buffer overflow in Libwebsockets
CVE-2026-114550
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.
Vulnerability class: Buffer Overflow
Published .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Libwebsockets — versions b4b5aed3903eaff09cd76a410f69bbe5dff66f8e
Weakness classification (CWE)
References
- www.zerodayinitiative.com/advisories/ZDI-26-792/ (x_research-advisory)
- github.com/warmcat/libwebsockets/commit/c9e8e1834d7f13038c82963086b90e2ee9c5b44c (vendor-advisory)
Frequently asked questions
- What is CVE-2026-114550?
- CVE-2026-114550 is a high-severity vulnerability in Libwebsockets, classified under Out-of-bounds Write. CVSS score: 8.1/10. Published 2026-11-04.
- How severe is CVE-2026-114550?
- High severity. CVSS v3 base score is 8.1 out of 10.