libwebsockets: libwebsockets HTTP/2 HPACK Path Header Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability
CVE-2026-19773 is fixed in 10 products on 1 platform, first by libwebsockets-evlib-ev 4.3.5-3ubuntu1.2+esm1, released September 15, 2026. It is not reported as exploited. Patch Radar priority: Urgent.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| libwebsockets · Debian 13.5 (trixie) | 4.3.5-1+deb13u3 | DEBIAN-CVE-2026-19773 | Sep 30, 2026 |
| libwebsockets · Debian 14 | 4.3.5-7 | DEBIAN-CVE-2026-19773 | Sep 30, 2026 |
| libwebsockets-evlib-ev · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets-evlib-ev 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-evlib-ev · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets-evlib-ev 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets-evlib-glib · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets-evlib-glib 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-evlib-glib · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets-evlib-glib 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets-evlib-uv · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets-evlib-uv 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-evlib-uv · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets-evlib-uv 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets-test-server · Ubuntu 18.04.6 LTS (bionic) | 2.0.3-3ubuntu0.1~esm1 | libwebsockets-test-server 2.0.3-3ubuntu0.1~esm1 | Oct 8, 2026 |
| libwebsockets-test-server · Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm3 | libwebsockets-test-server 3.2.1-3ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-test-server · Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1+esm2 | libwebsockets-test-server 4.0.20-2ubuntu1.1+esm2 | Oct 8, 2026 |
| libwebsockets-test-server · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets-test-server 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-test-server · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets-test-server 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets-test-server-common · Ubuntu 18.04.6 LTS (bionic) | 2.0.3-3ubuntu0.1~esm1 | libwebsockets-test-server-common 2.0.3-3ubuntu0.1~esm1 | Oct 8, 2026 |
| libwebsockets-test-server-common · Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm3 | libwebsockets-test-server-common 3.2.1-3ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-test-server-common · Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1+esm2 | libwebsockets-test-server-common 4.0.20-2ubuntu1.1+esm2 | Oct 8, 2026 |
| libwebsockets-test-server-common · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets-test-server-common 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets-test-server-common · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets-test-server-common 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets15 · Ubuntu 20.04 LTS (focal) | 3.2.1-3ubuntu0.1~esm3 | libwebsockets15 3.2.1-3ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets16 · Ubuntu 22.04.1 LTS (jammy) | 4.0.20-2ubuntu1.1+esm2 | libwebsockets16 4.0.20-2ubuntu1.1+esm2 | Oct 8, 2026 |
| libwebsockets19t64 · Ubuntu 24.04.5 LTS (noble) | 4.3.3-1.1ubuntu0.1~esm3 | libwebsockets19t64 4.3.3-1.1ubuntu0.1~esm3 | Oct 8, 2026 |
| libwebsockets19t64 · Ubuntu 26.04.1 LTS (resolute) | 4.3.5-3ubuntu1.2+esm1 | libwebsockets19t64 4.3.5-3ubuntu1.2+esm1 | Sep 15, 2026 |
| libwebsockets8 · Ubuntu 18.04.6 LTS (bionic) | 2.0.3-3ubuntu0.1~esm1 | libwebsockets8 2.0.3-3ubuntu0.1~esm1 | Oct 8, 2026 |
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