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GHSA-v9p9-hfj2-hcw8

Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation

Source: GitHub Advisory Database (reviewed) High CVE-2026-2229

Packages

EcosystemPackageAffectedFixed in
npm undici < 6.24.0 6.24.0
npm undici >= 7.0.0, < 7.24.0 7.24.0

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact The 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: 1. The `isValidClientWindowBits()` function only validates that the value contains ASCII digits, not that it falls within the valid range 8-15 2. The `createInflateRaw()` call is not wrapped in a try-catch block 3. The resulting exception propagates up through the call stack and crashes the Node.js process ### Patches _Has the problem been patched? What versions should users upgrade to?_ ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_

References

External links from the advisory. They lead to third-party sites.