CVE-2026-109855
CVE-2026-109855 · undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
This page contains facts from public vulnerability sources. Check the original advisory before updating.
undici is an HTTP client library for Node.js. In versions 8.11.0 and 8.11.1, its experimental WebSocket client, which is enabled by default when HTTP/2 is allowed, mishandles a failed WebSocket handshake over HTTP/2: the request is already marked completed, so the abort becomes a no-op and the underlying HTTP/2 stream is left open with no error listener. When a malicious server then destroys the connection, the orphaned stream emits an unhandled error and the Node.js process exits. A remote, unauthenticated server can therefore crash any client that opens a WebSocket to it over HTTP/2, resulting in a denial of service. The issue is fixed in undici 8.11.2, and users should upgrade to 8.11.2 or later. As a workaround, set allowH2 to false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers.
CVSS 7.5 · High · EPSS 0.3% · Fix available
- Published
- Updated
Stack: system
Affected products and versions
undici
- Versions
- ≥ 8.11.0, < 8.11.2: Affected (semver)
- 8.11.2: Not affected (semver)
Update to 8.11.2
node-undici Debian:14
- Versions
- 7.15.0+dfsg+~cs3.2.0-1
- 7.15.0+dfsg+~cs3.2.0-3
- 7.16.0+dfsg+~cs3.2.0-1
- 7.16.0+dfsg+~cs3.2.0-2
- 7.18.2+dfsg+~cs3.2.0-1
- 7.24.5+dfsg+~cs3.2.0-1
- 7.24.6+dfsg+~cs3.2.0-1
- 7.24.6+dfsg+~cs3.2.0-2
- 7.24.6+dfsg+~cs3.2.0-3
- 7.3.0+dfsg1+~cs24.12.11-1
- 7.3.0+dfsg1+~cs24.12.11-2
- 8.10.2+dfsg+~cs3.2.2-1
- 8.12.1+dfsg+~cs3.2.3-1
- 8.12.2+dfsg+~cs3.2.3-1
- 8.12.2+dfsg+~cs3.2.3-2
- 8.5.0+dfsg+~cs3.2.0-1
- 8.5.0+dfsg+~cs3.2.0-2
- 8.5.0+dfsg+~cs3.2.0-3
- 8.9.0+dfsg+~cs3.2.0-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
node-undici Ubuntu:24.04:LTS
- Versions
- 5.22.1+dfsg1+~cs20.10.10.2-1ubuntu1
- 5.26.3+dfsg1+~cs23.10.12-2
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
node-undici Ubuntu:26.10
- Versions
- 7.18.2+dfsg+~cs3.2.0-1build1
- 7.24.6+dfsg+~cs3.2.0-3
- 8.5.0+dfsg+~cs3.2.0-2
- 8.5.0+dfsg+~cs3.2.0-3
- 8.9.0+dfsg+~cs3.2.0-1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published
node-undici Ubuntu:26.04:LTS
- Versions
- 7.3.0+dfsg1+~cs24.12.11-2
- 7.16.0+dfsg+~cs3.2.0-2
- 7.18.2+dfsg+~cs3.2.0-1
- 7.18.2+dfsg+~cs3.2.0-1build1
- Affected ranges
- ECOSYSTEM: (−∞, +∞)
No fix published