CVE-2026-21710
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...
- Published
- Mar 30, 2026
- Updated
- Jul 15, 2026
- Assigning CNA
- hackerone
- Evidence observed
- Aug 25, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HModerate · next 30 days
- Percentile
- 97.9%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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**
Sources
1Proof-of-concept exploit for CVE-2026-21710, a Node.js HTTP request handling flaw causing uncaught TypeError via __proto__ header, leading to denial of service.
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