# CVE-2026-2229

## Summary

- **CVE ID:** CVE-2026-2229
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-248, CWE-1284
- **Published:** Mar 12, 2026
- **Last Modified:** Sep 14, 2026

## 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

## Affected Products

- undici — undici (< 6.24.0; 7.0.0 < 7.24.0)
- undici — undici (6.24.0: 7.24.0)

## References

- [CNA](https://github.com/nodejs/undici/security/advisories/GHSA-v9p9-hfj2-hcw8)
- [CNA](https://hackerone.com/reports/3487486)
- [CNA](https://cna.openjsf.org/security-advisories.html)
- [CNA](https://datatracker.ietf.org/doc/html/rfc7692)
- [CNA](https://nodejs.org/api/zlib.html#class-zlibinflateraw)
- [redhat-SADP](https://access.redhat.com/security/cve/CVE-2026-2229)
- [redhat-SADP](https://bugzilla.redhat.com/show_bug.cgi?id=2447143)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-2229.json)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:17789)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7310)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7080)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7675)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7123)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7670)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7983)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7302)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:7350)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:9742)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:13826)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:5807)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:21772)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:21931)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:34342)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:56431)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.87%
- **EPSS Percentile:** 57.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._