CVE-2026-21710

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 25.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-30 · updated 2026-08-19
Weakness: CWE-770

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**

Affected products

Node.js: through 20.20.1; from 22.0.0 through 22.22.1; from 24.0.0 through 24.14.0; from 25.0.0 through 25.8.1
Red Hat Enterprise Linux: 8.0, 9.0, 10.0
RedHat Enterprise Linux Eus: 9.4, 9.6, 10.0

References

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