This article explores the technical process of patch diffing and exploit development for a Use-After-Free (UAF) vulnerability within the Windows Desktop Window Manager (DWM). By analyzing the January 2026 Patch Tuesday updates for dwmcore.dll, the author identifies a logic error in the CSynchronousSuperWetInk destructor where a conditional check allows a dangling pointer to persist in the CSuperWetInkManager's internal vector.
The exploitation phase details a sophisticated "GetRECT" heap spray technique used to reclaim the freed memory with attacker-controlled data. To bypass Control Flow Guard (CFG) without an initial heap leak, the exploit leverages a novel gadget chain involving __fnINSTRING from user32.dll and CStdAsyncStubBuffer2_Disconnect from combase.dll. This chain facilitates a call to VirtualProtect to mark the spray buffer as executable, ultimately allowing for the execution of inline shellcode and achieving local privilege escalation to SYSTEM.
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