Ghidra < 12.1 - Heap-use-after-free in HighVariable::merge() during decompilation

Ghidra before 12.1 contains a heap-use-after-free vulnerability in the decompiler's HighVariable::merge() function during the variable merging pass. Attackers can trigger this vulnerability by crafting a binary that causes stale pointers in the HighIntersectTest::highedgemap cache to be dereferenced, reading and writing the flags field of freed heap memory when a user opens the binary in Ghidra's decompiler view.