EUVD-2026-11704
GHSA-v9p9-hfj2-hcw8
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the server_max_window_bits parameter in the permessage-deflate extension. When a WebSocket client connects to a server, it automatically advertises support for permessage-deflate compression. A malicious server can respond with an out-of-range server_max_window_bits value (outside zlib's valid range of 8-15). When the server subsequently sends a compressed frame, the client attempts to create a zlib InflateRaw instance with the invalid windowBits value, causing a synchronous RangeError exception that is not caught, resulting in immediate process termination. The vulnerability exists because: * The isValidClientWindowBits() function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 * The createInflateRaw() call is not wrapped in a try-catch block * The resulting exception propagates up through the call stack and crashes the Node.js process
Analysis
Node.js undici WebSocket client denial-of-service vulnerability allows remote attackers to crash the process by sending a malformed permessage-deflate compression parameter that bypasses validation and triggers an uncaught exception. The vulnerability exists because the client fails to properly validate the server_max_window_bits parameter before passing it to zlib, enabling any WebSocket server to terminate connected clients. …
Sign in for full analysis, threat intelligence, and remediation guidance.
Remediation
Within 24 hours: Identify all systems and applications using the undici WebSocket client and assess their criticality and exposure. Within 7 days: Implement compensating controls including WebSocket traffic filtering at the perimeter and disable permessage-deflate compression if operationally feasible. …
Sign in for detailed remediation steps.
Priority Score
Vendor Status
Share
External POC / Exploit Code
Leaving vuln.today