GHSA-v9p9-hfj2-hcw8 · Severity: high · Ecosystem: npm — Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation
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
Conclusion & alert: CVE-2026-2229 is rated Moderate Risk (43.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.49%). Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-06-15 | 0.19% | 0.49% | +0.30% |
| 2 | 2026-03-21 | 0.07% | 0.19% | +0.12% |
| 3 | 2026-03-13 | — | 0.07% | — |
Full EPSS history (3 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | ce714d77-add3-4f53-aff5-83d477b104bb |
GHSA-v9p9-hfj2-hcw8 · Severity: high · Ecosystem: npm — Undici has Unhandled Exception in WebSocket Client Due to Invalid server_max_window_bits Validation
| vendor | priority | summary | link |
|---|---|---|---|
alpine
|
— | CVE-2026-2229: 1 source package rows (nodejs); 10 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 10. | https://security.alpinelinux.org/vuln/CVE-2026-2229 |
debian
|
not yet assigned | CVE-2026-2229 not yet assigned priority: Debian including 1 source packages (node-undici), 4 status rows across 4 suites (bookworm, forky, sid, trixie): open 2, resolved 2. | https://security-tracker.debian.org/tracker/CVE-2026-2229 |
redhat
|
high | — | https://access.redhat.com/security/cve/CVE-2026-2229 |
ubuntu
|
medium | CVE-2026-2229 medium priority: Ubuntu including 1 source packages (node-undici), 4 status rows across 4 suites (jammy, noble, questing, upstream): needs-triage 3, DNE 1. | https://ubuntu.com/security/CVE-2026-2229 |
| URL | Tags |
|---|---|
| https://cna.openjsf.org/security-advisories.html | Vendor Advisory |
| https://datatracker.ietf.org/doc/html/rfc7692 | Technical Description |
| https://github.com/nodejs/undici/security/advisories/GHSA-v9p9-hfj2-hcw8 | Vendor Advisory |
| https://hackerone.com/reports/3487486 | Permissions Required |
| https://nodejs.org/api/zlib.html#class-zlibinflateraw | Technical Description |