CVE-2026-19773: libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
Last updated 7 October 2026
Other sources
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.
— Launchpad
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.
— ZDI
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/libwebsocketsto a version that resolves this vulnerability.Fixed in 4.3.5-1+deb13u3Fixed in 4.3.5-7
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
An attacker can exploit it remotely without authentication. Exploitation involves sending crafted HTTP/2 HPACK path-header data to an affected installation.
What is the likely impact if exploitation succeeds?
The out-of-bounds write can allow arbitrary code execution in the context of the current libwebsockets process. The listed CVSS vector indicates high potential impact to confidentiality, integrity, and availability.
Which deployments should be prioritized for investigation?
Prioritize affected libwebsockets installations that accept HTTP/2 traffic from untrusted or remote clients, because the flaw is in HTTP/2 HPACK path-header parsing and requires no authentication.