Vulnerability Instance

Next.js: Unbounded postponed resume buffering can lead to DoS
## Summary
A request containing the `next-resume: 1` header (corresponding with a PPR resume request) would buffer request bodies without consistently enforcing `maxPostponedStateSize` in certain setups. The previous mitigation protected minimal-mode deployments, but equivalent non-minimal deployments remained vulnerable to the same unbounded postponed resume-body buffering behavior.

## Impact
In applications using the App Router with Partial Prerendering capability enabled (via `experimental.ppr` or `cacheComponents`), an attacker could send oversized `next-resume` POST payloads that were buffered without consistent size enforcement in non-minimal deployments, causing excessive memory usage and potential denial of service.

## Patches
Fixed by enforcing size limits across all postponed-body buffering paths and erroring when limits are exceeded.  

## Workarounds
If upgrade is not immediately possible:
- Block requests containing the `next-resume` header, as this is never valid to be sent from an untrusted client.