A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Object.prototype` rather than `undefined`, causing `.push()` to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by `error` event listeners, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v2

This CVE is not in the KEV list.

Exploitation none

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Nodejs
  • Nodejs

No data.

No data.

References
Link Providers
https://www.spirityenterprise.com/pentest spirity
https://www.spirityenterprise.com/managed-detection-response spirity
https://nodejs.org/en/blog/vulnerability/march-2026-security-releases cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-21710 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-21710 cve-icon
History

Wed, 01 Apr 2026 02:15:00 +0000

Type Values Removed Values Added
Title Unhandled TypeError from __proto__ Header in Node.js HTTP Request Handling Node.js: Node.js: Denial of Service due to crafted HTTP `__proto__` header
First Time appeared Nodejs
Nodejs nodejs
Weaknesses CWE-20 CWE-843
Vendors & Products Nodejs
Nodejs nodejs
References
Metrics threat_severity

None

 cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Important

Tue, 31 Mar 2026 14:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-770
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 31 Mar 2026 03:00:00 +0000

Type Values Removed Values Added
Title Unhandled TypeError from __proto__ Header in Node.js HTTP Request Handling
Weaknesses CWE-20

Mon, 30 Mar 2026 19:30:00 +0000

Type Values Removed Values Added
Description A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Object.prototype` rather than `undefined`, causing `.push()` to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by `error` event listeners, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**
References
Metrics cvssV3_0

{'score': 7.5, 'vector': 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}
cve-icon MITRE

Status: PUBLISHED

Assigner: hackerone

Published:

Updated: 2026-03-31T13:55:23.719Z

Reserved: 2026-01-04T15:00:06.574Z

Link: CVE-2026-21710

cve-icon Vulnrichment

Updated: 2026-03-31T13:55:13.442Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-30T20:16:18.210

Modified: 2026-04-01T14:24:21.833

Link: CVE-2026-21710

cve-icon Redhat

Severity : Important

Publid Date: 2026-03-30T19:07:28Z

Links: CVE-2026-21710 - Bugzilla