CVE-2021-39178: Vercel Next.js

Medium severity, CVSS 6.1. EPSS: 1.1% chance of exploitation in the next 30 days.

Next.js is a React framework. Versions of Next.js between 10.0.0 and 11.0.0 contain a cross-site scripting vulnerability. In order for an instance to be affected by the vulnerability, the `next.config.js` file must have `images.domains` array assigned and the image host assigned in `images.domains` must allow user-provided SVG. If the `next.config.js` file has `images.loader` assigned to something other than default or the instance is deployed on Vercel, the instance is not affected by the vulnerability. The vulnerability is patched in Next.js version 11.1.1.

Affected products

• Vercel Next.js: from 10.0.0, before 11.1.1 (fixed in 11.1.1)

Published 2021-08-31. Last modified 2026-06-17.