Source: https://code.google.com/p/google-security-research/issues/detail?id=313
The PoC triggers a pool buffer overflow in win32k!vSolidFillRect. When using Special Pool we get the crash immediately on the overwrite. Without Special Pool we often get a crash in the same function, but sometimes it crashes in a different function (similar to another issue, however with a different offset). This might be a result of the memory corruption or an out-of-memory condition before the overflow is triggered. Debugger output for all three different crashes attached.
Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/38270.zip
