Next.js vulnerable to cache poisoning via collisions in React Server Component cache-busting

Impact

React Server Component responses can be vulnerable to cache poisoning in deployments that rely on shared caches with insufficient response partitioning. In affected conditions, collisions in the _rsc cache-busting value can allow an attacker to poison cache entries so users receive the wrong response variant for a given URL.

Fix

We strengthened the _rsc cache-busting mechanism to make practical collisions significantly harder and to better separate response variants that should not share cache entries.

Workarounds

If you cannot upgrade immediately, ensure intermediary caches correctly honor Vary for RSC-related request headers, or disable shared caching for affected RSC responses until you can deploy a patched release.