GHSA-qq8j-7v2v-3rwp: High severity npm/undici vulnerability

Q: Which deployments are exposed to this denial-of-service condition?

Applications using undici 8.11.0 or 8.11.1 and its experimental WebSocket client are exposed when they open a WebSocket connection to a malicious server over HTTP/2. HTTP/2 is enabled for these connections by default through allowH2: true.

Q: What does an attacker need to do to trigger the crash?

The attacker only needs to operate or control a server that the client connects to; no authentication or user interaction is required. The server must respond to the WebSocket upgrade over HTTP/2 with a response that fails handshake validation, then destroy the connection.

Q: What version resolves the issue?

Upgrade undici to version 8.11.2.

Published Oct 27, 2026

Impact

undici's experimental WebSocket client (enabled by default via allowH2: true) crashes the Node.js process when it connects to a malicious server over HTTP/2. If the server answers the WebSocket upgrade with a response that fails handshake validation, undici aborts the request, but the abort is a no-op because the request is already marked completed, so the underlying ClientHttp2Stream is left open with no error listener. When the server then destroys the connection, the orphaned stream emits an unhandled error and the process exits. A remote, unauthenticated server can therefore deny service to any client that opens a WebSocket to it over HTTP/2. undici 8.11.0 and 8.11.1 are affected; the regression was introduced in 8.11.0.

Patches

Upgrade to 8.11.2.

Workarounds

Set allowH2: false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers, until upgrading.

Affected Software

1 affected componentFixes available

npm/undici>=8.11.0<8.11.2

8.11.2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade npm/undici to a version that resolves this vulnerability.
Fixed in 8.11.2
Upgrade
Upgrade undici to a version that resolves this vulnerability.
Fixed in 8.11.2
Configuration
Set allowH2 to false to disable HTTP/2 for WebSocket connections.
undici experimental WebSocket client allowH2 = false
Compensating control
Avoid opening WebSocket connections to untrusted servers until upgrading.

Event History

Oct 27, 2026

Advisory Published

via GitHub·04:09 PM

Data Sourced

via GitHub·04:09 PM

DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

Which deployments are exposed to this denial-of-service condition?

Applications using undici 8.11.0 or 8.11.1 and its experimental WebSocket client are exposed when they open a WebSocket connection to a malicious server over HTTP/2. HTTP/2 is enabled for these connections by default through allowH2: true.

What does an attacker need to do to trigger the crash?

The attacker only needs to operate or control a server that the client connects to; no authentication or user interaction is required. The server must respond to the WebSocket upgrade over HTTP/2 with a response that fails handshake validation, then destroy the connection.

What can be done if upgrading immediately is not possible?

Set allowH2: false to disable HTTP/2 for WebSocket connections. Alternatively, avoid opening WebSocket connections to untrusted servers until the application can be upgraded.

What version resolves the issue?

Upgrade undici to version 8.11.2.

GHSA-qq8j-7v2v-3rwp: High severity npm/undici vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are exposed to this denial-of-service condition?

What does an attacker need to do to trigger the crash?

What can be done if upgrading immediately is not possible?

What version resolves the issue?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed to this denial-of-service condition?

What does an attacker need to do to trigger the crash?

What can be done if upgrading immediately is not possible?

What version resolves the issue?