static MagickBooleanType ExpandHeap(size_t size)
{
  DataSegmentInfo
    *segment_info;

  MagickBooleanType
    mapped;

  register ssize_t
    i;

  register void
    *block;

  size_t
    blocksize;

  void
    *segment;

  blocksize=((size+12*sizeof(size_t))+SegmentSize-1) & -SegmentSize;
  assert(memory_pool.number_segments < MaxSegments);
  segment=MapBlob(-1,IOMode,0,blocksize);
  mapped=segment != (void *) NULL ? MagickTrue : MagickFalse;
  if (segment == (void *) NULL)
    segment=(void *) memory_methods.acquire_memory_handler(blocksize);
  if (segment == (void *) NULL)
    return(MagickFalse);
  segment_info=(DataSegmentInfo *) free_segments;
  free_segments=segment_info->next;
  segment_info->mapped=mapped;
  segment_info->length=blocksize;
  segment_info->allocation=segment;
  segment_info->bound=(char *) segment+blocksize;
  i=(ssize_t) memory_pool.number_segments-1;
  for ( ; (i >= 0) && (memory_pool.segments[i]->allocation > segment); i--)
    memory_pool.segments[i+1]=memory_pool.segments[i];
  memory_pool.segments[i+1]=segment_info;
  memory_pool.number_segments++;
  size=blocksize-12*sizeof(size_t);
  block=(char *) segment_info->allocation+4*sizeof(size_t);
  *BlockHeader(block)=size | PreviousBlockBit;
  *BlockFooter(block,size)=size;
  InsertFreeBlock(block,AllocationPolicy(size));
  block=NextBlock(block);
  assert(block < segment_info->bound);
  *BlockHeader(block)=2*sizeof(size_t);
  *BlockHeader(NextBlock(block))=PreviousBlockBit;
  return(MagickTrue);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.