CVE catalog

CVE-2026-19773

Severity: Critical · CVSS 9.8CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: Sep 15, 2026, 7:17:00 PM UTC
Updated: Sep 15, 2026, 7:17:17 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.65% · Oct 25, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	libwebsockets	sid	`4.3.5-7`	fixed
Debian	libwebsockets	forky	`4.3.5-7`	fixed
Debian	libwebsockets	trixie	`4.3.5-1+deb13u2`	vulnerable
Debian	libwebsockets	trixie-security	`4.3.5-1+deb13u3`	fixed
Debian	libwebsockets	bookworm	`4.1.6-3`	vulnerable
Ubuntu	libwebsockets	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-dev	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-evlib-ev	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-evlib-glib	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-evlib-uv	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-test-server	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets-test-server-common	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets19t64	noble	`4.3.3-1.1ubuntu0.1~esm3`	fixed
Ubuntu	libwebsockets	pro	`4.3.5-1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1.1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1.2+esm1`	fixed
Ubuntu	libwebsockets	pro	`4.3.5-1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1.1`	vulnerable
Ubuntu	libwebsockets	pro	`4.3.5-3ubuntu1.2+esm1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	libwebsockets	source	sid	`4.3.5-7`	not yet assigned	Not reported	[1149178]
Debian	libwebsockets	source	forky	`4.3.5-7`	not yet assigned	Not reported	[1149178]
Debian	libwebsockets	source	trixie	`4.3.5-1+deb13u3`	not yet assigned	Not reported	[1149178]
Debian	libwebsockets	source	bookworm	`(unfixed)`	not yet assigned	Not reported	[1149178]
Ubuntu	libwebsockets	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-dev	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-evlib-ev	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-evlib-glib	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-evlib-uv	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-test-server	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets-test-server-common	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets19t64	deb	noble	`4.3.3-1.1ubuntu0.1~esm3`	Not reported	Not reported	Not reported
Ubuntu	libwebsockets	deb	pro	`4.3.5-3ubuntu1.2+esm1`	Not reported	USN-8893-1	Not reported
Ubuntu	libwebsockets	deb	pro	`4.3.5-3ubuntu1.2+esm1`	Not reported	UBUNTU-CVE-2026-19773	Not reported

[Debian bug #1149178]

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libwebsockets17]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-dev]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-evlib-ev]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-evlib-glib]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-evlib-uv]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-test-server]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · amd64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · arm64 · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
[libwebsockets-test-server-common]Affected
Source package: [libwebsockets]
Details (2)
- 4.1.6-3 · all · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12
- 4.1.6-3 · all · bookworm
  Affected
  nvd · libwebsockets · debian · bookworm; nvd · libwebsockets · debian · 12

[Debian 13 (Trixie)]

[libwebsockets19t64]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-dev]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-evlib-ev]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-evlib-glib]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-evlib-uv]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-test-server]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · amd64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · arm64 · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · amd64 · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
[libwebsockets-test-server-common]Affected
Source package: [libwebsockets]
Details (3)
- 4.3.5-1+deb13u1 · all · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u1 · all · trixie
  Affected · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13
- 4.3.5-1+deb13u3 · all · trixie-security
  Fixed · Fixed: 4.3.5-1+deb13u3
  nvd · libwebsockets · debian · 13

Observed: Oct 27, 2026, 6:28:44 AM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Ubuntu Security Notices (USN)]