Heap Out-of-Bounds Write via Integer Overflow in FlatBufferBuilder

### Summary
An integer overflow vulnerability exists in the C++ implementation of `FlatBufferBuilder`. When allocating space for vectors using functions such as `CreateUninitializedVector` or `make_space`, the library performs a multiplication of the requested number of elements by the element size without checking for integer overflow.

This allows an attacker to supply a maliciously crafted length value, resulting in a tiny memory allocation on the heap, followed by a massive Heap Out-of-Bounds Write (Heap Smash) when the application attempts to write the expected number of elements.

### Proof of Concept (PoC) & Fuzzing
I have written a standalone OSS-Fuzz target that reliably reproduces this memory corruption using libFuzzer and ASan.
* **OSS-Fuzz Integration:** The fuzzer has been officially reviewed and **approved** by the OSS-Fuzz maintainers in PR `google/oss-fuzz#15927`.

### Proposed Fix / Patch
I have already submitted a comprehensive patch that safely implements mathematical boundary checks across all allocation paths to eliminate this vulnerability class.
* **Patch PR:** #9145 (Currently awaiting maintainer review).

### Disclosure Context
This issue was originally reported to the Google OSS Vulnerability Reward Program (Ticket #525724852). After review, the VRP team authorized the public disclosure of this vulnerability on this repository.

Given the severe downstream impact on systems relying on `FlatBufferBuilder` for handling untrusted data, I strongly urge the maintainers to review and merge the existing patch (PR #9145) to secure the codebase.

Start by reviewing the FlatBufferBuilder allocation paths, especially CreateUninitializedVector and make_space, and compare the proposed boundary checks in PR #9145. Confirm the OSS-Fuzz target and ASan reproduction no longer trigger the reported heap out-of-bounds write.

Written by the indexing model from the issue text.