Cyber Resilience

CVE-2026-2229

Nodejs Undici ≤ 6.24.0

Published
12 March 2026
Modified
04 August 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0087 56th percentile
Risk Priority 59 floored blend · peak EPSS

Summary

CVE-2026-2229 is a high-severity Uncaught Exception (CWE-248) vulnerability in Nodejs Undici. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 44% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-2229 is a denial-of-service vulnerability in the undici WebSocket client, a component used within Node.js applications. The issue arises from improper validation of the server_max_window_bits parameter during negotiation of the permessage-deflate compression extension. When a client connects to a WebSocket server, it automatically advertises support for permessage-deflate. A malicious server can respond with an out-of-range value outside zlib's valid windowBits range of 8-15. Subsequent receipt of a compressed frame causes the client to invoke zlib's createInflateRaw() with the invalid parameter, triggering an uncaught RangeError exception. This stems from the isValidClientWindowBits() function checking only for ASCII digits rather than the valid range, combined with the absence of a try-catch block around the inflate creation, allowing the exception to propagate and crash the Node.js process. The vulnerability is rated 7.5 on CVSS 3.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and maps to CWE-248 and CWE-1284.

Any remote attacker controlling a WebSocket server can exploit this vulnerability when a vulnerable undici client initiates a connection. No authentication or user interaction is required. The attacker simply negotiates the permessage-deflate extension with an invalid server_max_window_bits value and sends a compressed frame, immediately causing a synchronous process crash and denial of service.

Mitigation details are available in advisories from the OpenJS Foundation CNA and the undici GitHub security advisory (GHSA-v9p9-hfj2-hcw8), along with the related HackerOne report (3487486). These reference the permessage-deflate RFC 7692 and Node.js zlib documentation for context on valid parameters.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

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…

more

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

CWE(s)
CWE-248CWE-1284

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-1528Same product: Nodejs Undici
CVE-2023-24807Same product: Nodejs Undici
CVE-2026-13697Same product: Nodejs Undici
CVE-2026-1525Same product: Nodejs Undici
CVE-2026-11525Same product: Nodejs Undici
CVE-2026-1527Same product: Nodejs Undici
CVE-2026-9679Same product: Nodejs Undici
CVE-2024-24750Same product: Nodejs Undici
CVE-2026-1526Same product: Nodejs Undici
CVE-2026-9675Same product: Nodejs Undici

Affected Assets

nodejs
undici
≤ 6.24.0 · 7.0.0 — 7.24.0

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V6.7.2
  • V1.4.2
  • V2.1.1
  • V2.2.1

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

SI-10 requires validity checks on information inputs, directly stopping acceptance of malformed quantities before they can be used.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles include robust exception management to keep the system in a defined state.

SC-24 Fail in Known State partial match

Fail-in-known-state reduces the impact when an uncaught exception occurs by preserving a safe condition.

SI-11 Error Handling partial match

Error handling requirements force structured catching and response to exceptions instead of allowing them to propagate uncaught.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices explicitly require structured exception handling to prevent uncaught exceptions from reaching production.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect uncaught exceptions before production deployment.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes exception-handling standards that reduce uncaught exceptions.

A.8.26 Application security requirements partial match
prevents

Application security requirements typically mandate robust error and exception handling.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles call for centralized, comprehensive exception management.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly require catching and handling exceptions to prevent crashes or leaks.

References