Adobe Flash - .SWF Out-of-Bounds Memory Read (2)

Source: https://code.google.com/p/google-security-research/issues/detail?id=362&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id

The following access violation was observed in the Adobe Flash Player plugin:

(1dec.1af0): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for FlashPlayer.exe - 
eax=00006261 ebx=00001501 ecx=010ae1e4 edx=00006262 esi=0736dda0 edi=05a860d0
eip=0044ae55 esp=010ae170 ebp=010ae564 iopl=0         nv up ei ng nz ac pe cy
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00210297
FlashPlayer!WinMainSandboxed+0x57aee:
0044ae55 803c3000        cmp     byte ptr [eax+esi],0       ds:002b:07374001=??

0:000> !address esi
[...]
Usage:                  <unknown>
Base Address:           06e60000
End Address:            07374000
Region Size:            00514000
State:                  00001000	MEM_COMMIT
Protect:                00000004	PAGE_READWRITE
Type:                   00020000	MEM_PRIVATE
Allocation Base:        06e60000
Allocation Protect:     00000001	PAGE_NOACCESS

0:000> db esi
0736dda0  8e 56 fa 1b 00 13 e3 85-00 0c 54 72 65 62 75 63  .V........Trebuc
0736ddb0  68 65 74 20 4d 53 3e 00-7e 00 80 00 9f 00 21 01  het MS>.~.....!.
0736ddc0  4c 01 76 01 85 01 97 01-e9 01 02 02 40 02 9a 02  L.v.........@...
0736ddd0  c4 02 1d 03 49 03 d8 03-26 04 4f 04 b5 04 fd 04  ....I...&.O.....
0736dde0  1d 05 39 05 90 05 b1 05-e2 05 f6 05 22 06 40 06  ..9.........".@.
0736ddf0  97 06 da 06 2d 07 94 07-ac 07 d8 07 02 08 21 08  ....-.........!.
0736de00  3f 08 af 08 fb 08 40 09-92 09 e2 09 1c 0a c9 0a  ?.....@.........
0736de10  00 0b 35 0b 5b 0b 77 0b-cd 0b 04 0c 52 0c 9d 0c  ..5.[.w.....R...

Notes:

- Reliably reproduces with latest Adobe Flash Player Projector for Windows and Google Chrome for Windows.

- The out-of-bounds read appears to be caused by an overly large index value (stored in the "EAX" register at the time of the crash) relative to a dynamically allocated buffer pointed to by "ESI".

- The memory under "ESI" contains a section of the input file starting at offset 0x50dda0.

- Attached samples: signal_sigsegv_7ffff6d8a235_3103_51dea5ced16249520f1fa0a7a63d7b36 (crashing file), 51dea5ced16249520f1fa0a7a63d7b36 (original file). The total difference between the two files is 19 bytes.

Proof of Concept:
https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/37857.zip