CVE-2026-2229

Name	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
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
node-undici (PTS)	bookworm	5.15.0+dfsg1+~cs20.10.9.3-1+deb12u4	vulnerable
	bookworm (security)	5.15.0+dfsg1+~cs20.10.9.3-1+deb12u3	vulnerable
	trixie	7.3.0+dfsg1+~cs24.12.11-1	vulnerable
	forky, sid	7.18.2+dfsg+~cs3.2.0-1	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
node-undici	source	(unstable)	(unfixed)

Notes

https://github.com/nodejs/undici/security/advisories/GHSA-v9p9-hfj2-hcw8
https://github.com/nodejs/undici/commit/e9e2997ed18bff6ae389712d5f0e169f8a6546a0 (v6.24.0)
https://github.com/nodejs/undici/commit/cb79c5704ac47e42ce01a72269994fc70e377536 (v7.24.0)