CVE-2026-21710

Name	CVE-2026-21710
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
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DSA-6183-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
nodejs (PTS)	bullseye	12.22.12~dfsg-1~deb11u4	vulnerable
	bullseye (security)	12.22.12~dfsg-1~deb11u7	vulnerable
	bookworm, bookworm (security)	18.20.4+dfsg-1~deb12u1	vulnerable
	trixie	20.19.2+dfsg-1	vulnerable
	trixie (security)	20.19.2+dfsg-1+deb13u2	fixed
	forky, sid	22.22.2+dfsg+~cs22.19.15-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
nodejs	source	trixie	20.19.2+dfsg-1+deb13u2		DSA-6183-1
nodejs	source	(unstable)	22.22.2+dfsg+~cs22.19.15-1

Notes

https://nodejs.org/en/blog/vulnerability/march-2026-security-releases#denial-of-service-via-__proto__-header-name-in-reqheadersdistinct-uncaught-typeerror-crashes-nodejs-process-cve-2026-21710---high
Fixed by: https://github.com/nodejs/node/commit/00ad47a28eb2e3dc0ff5610d58c53341acf3cf8d (v20.20.2)