---
id: CVE-2026-19773
title: >-
  libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code
  Execution Vulnerability
summary: >-
  libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code
  Execution Vulnerability. This vulnerability allows remote attackers to execute
  arbitrary code on affected installations of libwebsockets. Authentication is
  no…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-787
vendor: libwebsockets
product: libwebsockets
affected:
  - libwebsockets b4b5aed3903eaff09cd76a410f69bbe5dff66f8e
published: '2026-09-15'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T19:10:46.443'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19773'
references:
  - url: >-
      https://github.com/warmcat/libwebsockets/commit/824151862f37bc72f46d9a3e01d5b9408d313a0b
    label: zdi-disclosures@trendmicro.com
  - url: 'https://www.zerodayinitiative.com/advisories/ZDI-26-590/'
    label: zdi-disclosures@trendmicro.com
tags:
  - nvd
  - cve.org
epss: 0.00645
epssPercentile: 0.49182
zeroDay: true
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-15T19:20:31.411338Z'
ingestedAt: '2026-09-15T18:41:59.189Z'
---

## Overview

libwebsockets HTTP/2 HPACK Path Header Parsing 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 parsing of HTTP/2 HPACK path header. 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-31036.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.