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CVE-2026-2229— undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation

Quick assessment

Affected
undici undici
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

undici是Node.js开源的一个HTTP/1.1客户端。 undici存在安全漏洞，该漏洞源于对permessage-deflate扩展中server_max_window_bits参数验证不当，可能导致拒绝服务攻击。

CVSS 7.5 · High EPSS 0.87% · P58

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
undici undici < 6.24.0; 7.0.0 < 7.24.0 affected
6.24.0: 7.24.0 unaffected
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I. Basic Information for CVE-2026-2229

Vulnerability Information
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Vulnerability Title
undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation
Source: CVE Program / CVE List V5
Vulnerability 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 Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未捕获的异常
Source: CVE Program / CVE List V5
Vulnerability Title
undici 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
undici是Node.js开源的一个HTTP/1.1客户端。 undici存在安全漏洞，该漏洞源于对permessage-deflate扩展中server_max_window_bits参数验证不当，可能导致拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
undici undici < 6.24.0; 7.0.0 < 7.24.0 -

II. Public POCs for CVE-2026-2229

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III. Intelligence Information for CVE-2026-2229

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Vendor Advisories for CVE-2026-2229 (1)

Vendor Pages for CVE-2026-2229 (1)

Other References for CVE-2026-2229 (1)

Same Patch Batch · undici · 2026-03-12 · 6 CVEs total

CVE-2026-1526 7.5 HIGH undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflat
CVE-2026-1528 7.5 HIGH undici is vulnerable to Malicious WebSocket 64-bit length overflows undici parser and cras
CVE-2026-1525 6.5 MEDIUM undici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Respon
CVE-2026-2581 5.9 MEDIUM undici is vulnerable to Unbounded Memory Consumption in in Undici's DeduplicationHandler v
CVE-2026-1527 4.6 MEDIUM undici is vulnerable to CRLF Injection via upgrade option

IV. Related Vulnerabilities

Same product: undici
Same vendor: undici
Same weakness: CWE-248

V. Comments for CVE-2026-2229

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