CVE-2026-2229

ImpactThe undici WebSocket client is vulnerable to a denial-of-service attack due to improper validation of the servermaxwindowbits 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 servermaxwindowbits 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

References

Affected packages

Git /

Affected ranges

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-2229.json"

unresolved_ranges

[
    {
        "events": [
            {
                "introduced": "0"
            },
            {
                "last_affected": "the"
            }
        ]
    }
]