GHSA-rfgv-xxqx-mfg5

undici vulnerable to Denial of Service via unrequested WebSocket subprotocol

At a glance

Published
Updated
CVE
CVE-2026-19534
CVSS_V3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Description

### Impact The undici WebSocket client throws an uncaught `TypeError` during the opening handshake when a server's `101` response includes a `Sec-WebSocket-Protocol` header that the client never requested. The throw occurs in a `queueMicrotask` callback with no surrounding `try`/`catch`, so it propagates as an uncaught exception and terminates the Node.js process. This is a remote, unauthenticated denial of service against any application that opens a WebSocket to an attacker controlled or compromised server, or over a plaintext `ws://` connection subject to a machine-in-the-middle. It affects the default `new WebSocket(url)` usage, where no subprotocol is requested. Per RFC 6455 section 4.1, an unrequested subprotocol must fail the connection, not crash it. All releases starting at undici 6.7.0 are affected. ### Patches Upgrade to undici 6.28.1, 7.29.1, or 8.10.2. ### Workarounds No workaround is available. The fix must be applied through an upgrade.

Affected packages

PackageVersions
npm · undiciintroduced 6.7.0, fixed 6.28.1
npm · undiciintroduced 7.0.0, fixed 7.29.1
npm · undiciintroduced 8.0.0, fixed 8.10.2

References

Sources

SourceLicence
OSV.devCC-BY 4.0 — GitHub Advisory Database