CVE-2026-2229
Description
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
CVSS Base Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected Products
| Vendor | Product | Version | Status |
|---|---|---|---|
| undici | undici | < 6.24.0; 7.0.0 < 7.24.0 | affected |
| undici | undici | 6.24.0: 7.24.0 | unaffected |
Credits
- Matteo Collina(remediation developer)
- Ulises Gascón(remediation reviewer)
- Rafael Gonzaga(remediation reviewer)
- Ethan Arrowood(remediation reviewer)
- Aisle Research(reporter)