CVE-2026-21710: high-severity vulnerability in nodejs node
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No sign of exploitation. No public exploitation artifact known so far.
A Node.js HTTP server crashes with an unhandled error when receiving a request with a header named `__proto__` if the application reads `req.headersDistinct`. This denial-of-service flaw cannot be caught by normal error handlers, forcing developers to add extra protection around header access.
The vulnerability exploits prototype pollution via HTTP header injection; when `__proto__` header is present and `req.headersDistinct` is accessed, the property getter resolves `dest["__proto__"]` to `Object.prototype` instead of undefined, causing a synchronous TypeError when `.push()` is called on the prototype object. This exception cannot be intercepted by error event listeners, enabling unauthenticated DoS against Node.js HTTP servers on versions 20.x, 22.x, 24.x, and 25.x.
In the same product, most dangerous first.