Next.js Cache Poisoning

Impact

By sending a crafted HTTP request, it is possible to poison the cache of a non-dynamic server-side rendered route in the pages router (this does not affect the app router). When this crafted request is sent it could coerce Next.js to cache a route that is meant to not be cached and send a Cache-Control: s-maxage=1, stale-while-revalidate header which some upstream CDNs may cache as well.

To be potentially affected all of the following must apply:

• Next.js between 13.5.1 and 14.2.9
• Using pages router
• Using non-dynamic server-side rendered routes e.g. pages/dashboard.tsx not pages/blog/[slug].tsx

The below configurations are unaffected:

• Deployments using only app router
• Deployments on Vercel are not affected

Patches

This vulnerability was resolved in Next.js v13.5.7, v14.2.10, and later. We recommend upgrading regardless of whether you can reproduce the issue or not.

Workarounds

There are no official or recommended workarounds for this issue, we recommend that users patch to a safe version.

Credits

• Allam Rachid (zhero_)
• Henry Chen