CVE-2026-19773 libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
Remote attackers can execute arbitrary code via an out-of-bounds write in libwebsockets HTTP/2 HPACK path header parsing without authentication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-19773?
CVE-2026-19773 is a critical memory corruption vulnerability in libwebsockets, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-787
Which versions are affected by CVE-2026-19773?
How do I fix CVE-2026-19773?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-19773 being exploited?
There is no known exploitation of CVE-2026-19773 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-19773, GHSA-r4m8-276f-3r2f, UBUNTU-CVE-2026-19773, USN-8893-1.