Node.js HTTP __proto__ Header Injection Causing Uncaught TypeError
CVE-2026-21710 Published on March 30, 2026
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**
Weakness Type
Allocation of Resources Without Limits or Throttling
The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
Affected Versions
nodejs node:- Version 20.20.1, <= 20.20.1 is affected.
- Version 22.22.1, <= 22.22.1 is affected.
- Version 24.14.0, <= 24.14.0 is affected.
- Version 25.8.1, <= 25.8.1 is affected.
- Version 4.0 and below 4.* is affected.
- Version 5.0 and below 5.* is affected.
- Version 6.0 and below 6.* is affected.
- Version 7.0 and below 7.* is affected.
- Version 8.0 and below 8.* is affected.
- Version 9.0 and below 9.* is affected.
- Version 10.0 and below 10.* is affected.
- Version 11.0 and below 11.* is affected.
- Version 12.0 and below 12.* is affected.
- Version 13.0 and below 13.* is affected.
- Version 14.0 and below 14.* is affected.
- Version 15.0 and below 15.* is affected.
- Version 16.0 and below 16.* is affected.
- Version 17.0 and below 17.* is affected.
- Version 18.0 and below 18.* is affected.
- Version 19.0 and below 19.* is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.