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Vulnerability record · CVE-2026-19773 · published 15 September 2026

CVE-2026-19773: Out-of-bounds write vulnerability

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.

9.8 CVSS 3.0 Critical EPSS 0.65% · top 51.1% CWE-787 · Out-of-bounds write Awaiting Analysis
9.8CVSS 3.0 base score
0.65%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
18 Sep 2026Last modified by NVD

Description

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.

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

LinkTags
https://github.com/warmcat/libwebsockets/commit/824151862f37bc72f46d9a3e01d5b9408d313a0b
https://www.zerodayinitiative.com/advisories/ZDI-26-590/

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Source: NIST National Vulnerability Database (record CVE-2026-19773), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.