CVE-2026-19534

The record

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 WebSocket connection sends no subprotocol, but if the server's 101 response includes a Sec-WebSocket-Protocol header, undici dereferences a null value while checking it against the requested list and throws an uncaught TypeError. Because that code runs inside a microtask with no surrounding error handling, the exception propagates and terminates the process under Node's default behavior, instead of gracefully failing the connection as required by the WebSocket protocol. Any application that opens a WebSocket to an attacker-controlled or compromised server, or over a plaintext connection subject to a machine-in-the-middle, can be crashed remotely without authentication in the default configuration. This affects undici versions from 6.7.0 up to 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.

Affected packages

Related vulnerabilities

• CVE-2026-100347 kin-openapi is a Go project for handling OpenAPI files. CWE-248
• CVE-2026-102599 Socket.IO enables bidirectional and low-latency communication for every platform. CWE-248
• CVE-2026-107382 MariaDB Connector/Node.js is used to connect applications developed on Node.js to MariaDB… CWE-248
• CVE-2026-106122 The RabbitMQ Java client library allows Java and JVM-based applications to connect to and… CWE-248
• CVE-2026-105757 vLLM is an inference and serving engine for large language models. CWE-248
• CVE-2026-105756 vLLM is an inference and serving engine for large language models. CWE-248
• CVE-2026-103387 A weakness has been identified in garycourt uri-js up to 4.4.1. CWE-248
• CVE-2026-102281 Nest is a framework for building scalable Node.js server-side applications. CWE-248