Next.js: Unbounded next/image disk cache growth can exhaust storage

Summary

The default Next.js image optimization disk cache (/_next/image) did not have a configurable upper bound, allowing unbounded cache growth.

Impact

An attacker could generate many unique image-optimization variants and exhaust disk space, causing denial of service. Note that this does not impact platforms that have their own image optimization capabilities, such as Vercel.

Patches

Fixed by adding an LRU-backed disk cache with images.maximumDiskCacheSize, including eviction of least-recently-used entries when the limit is exceeded. Setting maximumDiskCacheSize: 0 disables disk caching.

Workarounds

If upgrade is not immediately possible:

• Periodically clean .next/cache/images.
• Reduce variant cardinality (e.g., tighten values for images.localPatterns, images.remotePatterns, and images.qualities)