next.js cache leak across root param values in nested 'use cache' functions

Impact

With Cache Components enabled (cacheComponents: true), a 'use cache' function that calls another 'use cache' function that reads a root param can be keyed incorrectly when the inner call is served from an existing entry: the enclosing function's cache key then omits that root param. The enclosing entry is written once and reused for all root param values, so a response for one root param value can serve content produced for a different value — whether the page is prerendered at build time or at runtime, or rendered dynamically. Shared cache headers let downstream caches redistribute the content further.

What values are leaked cannot be attacker controlled. Which value's content is served depends only on which invocation wrote the entry first.

Workarounds

There are no known workarounds. Apps should upgrade to the patched version as soon as possible.