  tt_cmap8_validate( FT_Byte*      table,
                     FT_Validator  valid )
  {
    FT_Byte*   p = table + 4;
    FT_Byte*   is32;
    FT_UInt32  length;
    FT_UInt32  num_groups;


    if ( table + 16 + 8192 > valid->limit )
      FT_INVALID_TOO_SHORT;

    length = TT_NEXT_ULONG( p );
    if ( length > (FT_UInt32)( valid->limit - table ) || length < 8192 + 16 )
      FT_INVALID_TOO_SHORT;

    is32       = table + 12;
     p          = is32  + 8192;          /* skip `is32' array */
     num_groups = TT_NEXT_ULONG( p );
 
    if ( p + num_groups * 12 > valid->limit )
       FT_INVALID_TOO_SHORT;
 
     /* check groups, they must be in increasing order */
      FT_UInt32  n, start, end, start_id, count, last = 0;


      for ( n = 0; n < num_groups; n++ )
      {
        FT_UInt   hi, lo;


        start    = TT_NEXT_ULONG( p );
        end      = TT_NEXT_ULONG( p );
        start_id = TT_NEXT_ULONG( p );

        if ( start > end )
          FT_INVALID_DATA;

        if ( n > 0 && start <= last )
          FT_INVALID_DATA;

 
         if ( valid->level >= FT_VALIDATE_TIGHT )
         {
          if ( start_id + end - start >= TT_VALID_GLYPH_COUNT( valid ) )
             FT_INVALID_GLYPH_ID;
 
           count = (FT_UInt32)( end - start + 1 );
            {
              hi = (FT_UInt)( start >> 16 );
              lo = (FT_UInt)( start & 0xFFFFU );

              if ( (is32[hi >> 3] & ( 0x80 >> ( hi & 7 ) ) ) == 0 )
                FT_INVALID_DATA;

              if ( (is32[lo >> 3] & ( 0x80 >> ( lo & 7 ) ) ) == 0 )
                FT_INVALID_DATA;
            }
          }
          else
          {
            /* start_hi == 0; check that is32[i] is 0 for each i in */
            /* the range [start..end]                               */

            /* end_hi cannot be != 0! */
            if ( end & ~0xFFFFU )
              FT_INVALID_DATA;

            for ( ; count > 0; count--, start++ )
            {
              lo = (FT_UInt)( start & 0xFFFFU );

              if ( (is32[lo >> 3] & ( 0x80 >> ( lo & 7 ) ) ) != 0 )
                FT_INVALID_DATA;
            }
          }
        }

        last = end;
      }

The product reads data past the end, or before the beginning, of the intended buffer.