undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
### 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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-19534US | — | — | ||
undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested. A default WebSoc… | ||||
references
External citations — patches, advisories, analysis.
- https://cna.openjsf.org/security-advisories.htmlWEB
- https://github.com/nodejs/undiciPACKAGE
- https://github.com/nodejs/undici/commit/2af0faf88b906d3127a360c3ac75164c0f95e5a5WEB
- https://github.com/nodejs/undici/commit/6615e0175e9b635bcd2e3e87a47daa82f6f5b728WEB
- https://github.com/nodejs/undici/commit/66e12816064cf3068f63bd134748b7fc4e779badWEB
- https://github.com/nodejs/undici/releases/tag/v6.28.1WEB
- https://github.com/nodejs/undici/releases/tag/v7.29.1WEB
- https://github.com/nodejs/undici/releases/tag/v8.10.2WEB
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