In short
- CVE-2026-2229 is a HIGH (CVSS 7.5) vulnerability affecting undici (nodejs), undici.
- Chance of exploitation in the next 30 days (EPSS): 0.91%, higher than 60.0% of all vulnerabilities.
- Fix: update to 7.24.0, 6.24.0 or later.
| Package | Affected versions | Patched versions |
|---|
| undici | ≥ 7.0.0, < 7.24.0< 6.24.0
| 7.24.06.24.0
|
| undici npm | ≥ 7.0.0, < 7.24.0< 6.24.0
| 7.24.06.24.0
|
Description
Impact
The 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
Patches
Has the problem been patched? What versions should users upgrade to?
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
NVD 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
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