ZDI-26-590: 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.
Other sources
This vulnerability allows remote attackers to execute arbitrary code on affected installations of libwebsockets. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 9.8. The following CVEs are assigned: CVE-2026-19773.
— ZDI
Affected Software
Event History
Frequently Asked Questions
Which deployments should be prioritized for investigation and remediation?
Affected libwebsockets installations that can be reached by remote attackers should be prioritized, because exploitation does not require authentication and can result in arbitrary code execution.
What identifier should be used to track this issue across vulnerability-management systems?
Track the issue as CVE-2026-19773. The advisory identifier is ZDI-26-590.