Impact

Vulnerable code could allow a bad actor to trigger a denial of service attack for anyone running a Next.js app at version >= 12.0.0, and using i18n functionality.

- Affected: All of the following must be true to be affected by this CVE - Next.js versions above v12.0.0 - Using next start or a custom server - Using the built-in i18n support - Not affected: - Deployments on Vercel (vercel.com) are not affected along with similar environments where invalid requests are filtered before reaching Next.js.

Patches

A patch has been released, next@12.0.9, that mitigates this issue. We recommend all affected users upgrade as soon as possible.

Workarounds

We recommend upgrading whether you can reproduce or not although you can ensure /${locale}/next/ is blocked from reaching the Next.js instance until you upgrade.

For more information

If you have any questions or comments about this advisory: Open an issue in next Email us at security@vercel.com

Next.js is a React framework. In versions of Next.js prior to 12.0.5 or 11.1.3, invalid or malformed URLs could lead to a server crash. In order to be affected by this issue, the deployment must use Next.js versions above 11.1.0 and below 12.0.5, Node.js above 15.0.0, and next start or a custom server. Deployments on Vercel are not affected, along with similar environments where invalid requests are filtered before reaching Next.js. Versions 12.0.5 and 11.1.3 contain patches for this issue.