Steps to reproduce:
1. Open the “user’s attached project”
2. Create a 3D GameObject in the scene
3. Select the created GameObject and add the “Update Mesh” script Component through the Inspector
4. Under the “Update Mesh” component press the “Update Mesh” button
5. Observe the crash

Reproducible with: 6000.0.51f1, 6000.1.6f1, 6000.2.0b5
Couldn’t test with: 2021.3.52f1, 2022.3.63f1 (due to compiler errors)

Reproducible on: macOS 15.5 (M1 Max), Windows 11 (by the user)
Not reproducible on: no other environment tested

First few lines of StackTrace:
{noformat}
#0 0x000001059afb5c in block_merge_next
#1 0x000001032b3960 in DynamicHeapAllocator::Deallocate(void)
#2 0x000001032c08c4 in DualThreadAllocator<DynamicHeapAllocator>::TryDeallocate(void)
#3 0x000001032bae48 in MemoryManager::TryDeallocateWithLabel(void, MemLabelId, char const, int)
#4 0x000001032b5768 in free_alloc_internal(void, MemLabelId const&, char const, int){noformat}
{noformat}
0x00007FFC580EA54C (Unity) block_locate_free
0x00007FFC580EACF2 (Unity) tlsf_memalign
0x00007FFC55C4DD6B (Unity) DynamicHeapAllocator::Allocate
0x00007FFC55C5CE75 (Unity) DualThreadAllocator<DynamicHeapAllocator>::Allocate
0x00007FFC55C4E59D (Unity) MemoryManager::Allocate{noformat}

Workaround:
The issue can be mitigated by ensuring that SubMeshDescriptor.baseVertex does not result in out of bound indexing of the vertex buffer. Validation and error handling has been improved in versions where this case is resolved as fixed.