static Image *ReadMATImageV4(const ImageInfo *image_info,Image *image,
  ExceptionInfo *exception)
{
  typedef struct {
    unsigned char Type[4];
    unsigned int nRows;
    unsigned int nCols;
    unsigned int imagf;
    unsigned int nameLen;
  } MAT4_HDR;

  long
    ldblk;

  EndianType
    endian;

  Image
    *rotate_image;

  MagickBooleanType
    status;

  MAT4_HDR
    HDR;

  QuantumInfo
    *quantum_info;

  QuantumFormatType
    format_type;

  register ssize_t
    i;

  ssize_t
    count,
    y;

  unsigned char
    *pixels;

  unsigned int
    depth;


  quantum_info=(QuantumInfo *) NULL;
  (void) SeekBlob(image,0,SEEK_SET);
  while (EOFBlob(image) != MagickFalse)
  {
    /*
     Object parser loop.
    */
    ldblk=ReadBlobLSBLong(image);
    if ((ldblk > 9999) || (ldblk < 0))
      break;
    HDR.Type[3]=ldblk % 10; ldblk /= 10;  /* T digit */
    HDR.Type[2]=ldblk % 10; ldblk /= 10;  /* P digit */
    HDR.Type[1]=ldblk % 10; ldblk /= 10;  /* O digit */
    HDR.Type[0]=ldblk;        /* M digit */
    if (HDR.Type[3] != 0)
      break;  /* Data format */
    if (HDR.Type[2] != 0)
      break;  /* Always 0 */
    if (HDR.Type[0] == 0)
      {
        HDR.nRows=ReadBlobLSBLong(image);
        HDR.nCols=ReadBlobLSBLong(image);
        HDR.imagf=ReadBlobLSBLong(image);
        HDR.nameLen=ReadBlobLSBLong(image);
        endian=LSBEndian;
      }
    else
      {
        HDR.nRows=ReadBlobMSBLong(image);
        HDR.nCols=ReadBlobMSBLong(image);
        HDR.imagf=ReadBlobMSBLong(image);
        HDR.nameLen=ReadBlobMSBLong(image);
        endian=MSBEndian;
      }
    if ((HDR.imagf != 0) && (HDR.imagf != 1))
      break;
    if (HDR.nameLen > 0xFFFF)
      return((Image *) NULL);
    for (i=0; i < (ssize_t) HDR.nameLen; i++)
    {
      int
        byte;

      /*
        Skip matrix name.
      */
      byte=ReadBlobByte(image);
      if (byte == EOF)
        {
          ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",
            image->filename);
          break;
        }
    }
    image->columns=(size_t) HDR.nRows;
    image->rows=(size_t) HDR.nCols;
    SetImageColorspace(image,GRAYColorspace,exception);
    if (image_info->ping != MagickFalse)
      {
        Swap(image->columns,image->rows);
        return(image);
      }
    status=SetImageExtent(image,image->columns,image->rows,exception);
    if (status == MagickFalse)
      return((Image *) NULL);
    quantum_info=AcquireQuantumInfo(image_info,image);
    if (quantum_info == (QuantumInfo *) NULL)
      return((Image *) NULL);
    switch(HDR.Type[1])
    {
      case 0:
        format_type=FloatingPointQuantumFormat;
        depth=64;
        break;
      case 1:
        format_type=FloatingPointQuantumFormat;
        depth=32;
        break;
      case 2:
        format_type=UnsignedQuantumFormat;
        depth=16;
        break;
      case 3:
        format_type=SignedQuantumFormat;
        depth=16;
        break;
      case 4:
        format_type=UnsignedQuantumFormat;
        depth=8;
        break;
      default:
        format_type=UnsignedQuantumFormat;
        depth=8;
        break;
    }
    image->depth=depth;
    if (HDR.Type[0] != 0)
      SetQuantumEndian(image,quantum_info,MSBEndian);
    status=SetQuantumFormat(image,quantum_info,format_type);
    status=SetQuantumDepth(image,quantum_info,depth);
    status=SetQuantumEndian(image,quantum_info,endian);
    SetQuantumScale(quantum_info,1.0);
    pixels=(unsigned char *) GetQuantumPixels(quantum_info);
    for (y=0; y < (ssize_t) image->rows; y++)
    {
      register Quantum
        *magick_restrict q;

      count=ReadBlob(image,depth/8*image->columns,(char *) pixels);
      if (count == -1)
        break;
      q=QueueAuthenticPixels(image,0,image->rows-y-1,image->columns,1,
        exception);
      if (q == (Quantum *) NULL)
        break;
      (void) ImportQuantumPixels(image,(CacheView *) NULL,quantum_info,
        GrayQuantum,pixels,exception);
      if ((HDR.Type[1] == 2) || (HDR.Type[1] == 3))
        FixSignedValues(image,q,(int) image->columns);
      if (SyncAuthenticPixels(image,exception) == MagickFalse)
        break;
      if (image->previous == (Image *) NULL)
        {
          status=SetImageProgress(image,LoadImageTag,(MagickOffsetType) y,
            image->rows);
          if (status == MagickFalse)
            break;
        }
    }
    if (HDR.imagf == 1)
      for (y=0; y < (ssize_t) image->rows; y++)
      {
        /*
          Read complex pixels.
        */
        count=ReadBlob(image,depth/8*image->columns,(char *) pixels);
        if (count == -1)
          break;
        if (HDR.Type[1] == 0)
          InsertComplexDoubleRow(image,(double *) pixels,y,0,0,exception);
        else
          InsertComplexFloatRow(image,(float *) pixels,y,0,0,exception);
      }
    if (quantum_info != (QuantumInfo *) NULL)
      quantum_info=DestroyQuantumInfo(quantum_info);
    rotate_image=RotateImage(image,90.0,exception);
    if (rotate_image != (Image *) NULL)
      {
        image=DestroyImage(image);
        image=rotate_image;
      }
    if (EOFBlob(image) != MagickFalse)
      {
        ThrowFileException(exception,CorruptImageError,"UnexpectedEndOfFile",
          image->filename);
        break;
      }
    /*
      Proceed to next image.
    */
    if (image_info->number_scenes != 0)
      if (image->scene >= (image_info->scene+image_info->number_scenes-1))
        break;
    /*
      Allocate next image structure.
    */
    AcquireNextImage(image_info,image,exception);
    if (GetNextImageInList(image) == (Image *) NULL)
      {
        image=DestroyImageList(image);
        return((Image *) NULL);
      }
    image=SyncNextImageInList(image);
    status=SetImageProgress(image,LoadImagesTag,TellBlob(image),
      GetBlobSize(image));
    if (status == MagickFalse)
      break;
  }
  (void) CloseBlob(image);
  return(GetFirstImageInList(image));
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.