VulnerabilityModified

CVE-2026-2229

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.

HIGH 7.5EPSS 0.87%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.87%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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

CVSS 3.1: 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.87% probability · 57th percentile
CISA KEV: Not listed
Weakness: CWE-248, CWE-1284
Affected: nodejs/undici
Source: ce714d77-add3-4f53-aff5-83d477b104bb

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.