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RealNetworks RealPlayer/RealOne Player/Helix Player Remote Heap Corruption
From: "Piotr Bania" <bania.piotr () gmail com>
Date: Fri, 26 Oct 2007 06:10:24 +0200

RealNetworks RealPlayer/RealOne Player/Helix Player Remote Heap Corruption
by Piotr Bania <bania.piotr () gmail com>

Original url (and formatting):

Severity:           Important/Critical - Potencial remote code execution.

Software affected:  tested on RealPlayer Version 10.5(newest?) + Harmony

Timeline:  02/09/2006 - Advisory sent to RealNetworks
           05/09/2006 - Initial vendor response
           25/10/2007 - Advisory released


Real*Player* is surely one of the most popular media players nowadays
with over a 200 million of users worldwide.


The problem exists when Real*Player* parses a special crafted .mov file.
Here is the vulnerable code:

--//- snip ----//-----------------------------------------------------

62A70598   8A47 05          MOV AL,BYTE PTR DS:[EDI+5]      ; al=controled
by attacker
62A7059B   8A67 04          MOV AH,BYTE PTR DS:[EDI+4]      ; ah=controled
by attacker
62A7059E   66:3B86 AE000000 CMP AX,WORD PTR DS:[ESI+AE]     ; below 2?
62A705A5   73 11            JNB SHORT 62A705B8              ; not signed
compare, assume:taken!
62A705A7   8B8E B0000000    MOV ECX,DWORD PTR DS:[ESI+B0]
62A705AD   25 FFFF0000      AND EAX,0FFFF
62A705B2   66:8B0441        MOV AX,WORD PTR DS:[ECX+EAX*2]
62A705B6   EB 05            JMP SHORT 62A705BD
62A705B8   B8 FFFF0000      MOV EAX,0FFFF                   ; eax=0xFFFF
62A705BD   33D2             XOR EDX,EDX                     ; edx=0
62A705BF   33C9             XOR ECX,ECX                     ; ecx=0

62A705C1   8A77 06          MOV DH,BYTE PTR DS:[EDI+6]      ; dh=controled
by attacker
62A705C4   8A6F 08          MOV CH,BYTE PTR DS:[EDI+8]      ; ch=controled
by attacker
62A705C7   8A57 07          MOV DL,BYTE PTR DS:[EDI+7]`     ; dl=controled
by attacker
62A705CA   81E1 FFFF0000    AND ECX,0FFFF                   ; leave only CX
62A705D0   C1E2 10          SHL EDX,10                      ; rotation
62A705D3   0BD1             OR EDX,ECX                      ; power up the
bits given by ecx
62A705D5   33C9             XOR ECX,ECX                     ; ecx=0
62A705D7   8A4F 09          MOV CL,BYTE PTR DS:[EDI+9]      ; cl=controled
by attacker
62A705DA   0BD1             OR EDX,ECX                      ; power up some
62A705DC   8B8E 8A000000    MOV ECX,DWORD PTR DS:[ESI+8A]
62A705E2   85C9             TEST ECX,ECX                    ; ecx=0? =>
take the jump
62A705E4   74 0F            JE SHORT 62A705F5
62A705E6   3956 48          CMP DWORD PTR DS:[ESI+48],EDX
62A705E9   76 0A            JBE SHORT 62A705F5
62A705EB   C786 8E000000 01>MOV DWORD PTR DS:[ESI+8E],1

62A705F5   8956 48          MOV DWORD PTR DS:[ESI+48],EDX   ; store edx
62A705F8   8B8E 8A000000    MOV ECX,DWORD PTR DS:[ESI+8A]   ; ecx = 0
62A705FE   41               INC ECX                         ; ecx++
62A705FF   25 FFFF0000      AND EAX,0FFFF                   ; leave the AX
value (0xffff)
62A70604   898E 8A000000    MOV DWORD PTR DS:[ESI+8A],ECX   ; [esi+0x8a]=1
62A7060A   8BC8             MOV ECX,EAX                     ; ecx=0xffff
62A7060C   C1E0 05          SHL EAX,5                       ; eax=0x1FFFE0
62A7060F   2BC1             SUB EAX,ECX                     ; eax-0xffff =
62A70611   8B8E 9A000000    MOV ECX,DWORD PTR DS:[ESI+9A]   ; ecx=heap mem
62A70617   D1E0             SHL EAX,1                       ;
62A70619   03C8             ADD ECX,EAX                     ; ecx=ecx+eax
(memory location)
62A7061B   8379 36 00       CMP DWORD PTR DS:[ECX+36],0
62A7061F   75 1F            JNZ SHORT 62A70640
62A70621   8951 24          MOV DWORD PTR DS:[ECX+24],EDX   ; ** corruption

--//- snip ----//-----------------------------------------------------

The instruction at 0x62A70621 stores the value of EDX register (controled
by attacker)
to the location at [ECX+0x24]. The value of [ECX+0x24] is not completly
by attacker but it seems it is possible to rotate it when value of AX at
is below 2. If memory at [ECX+0x24] contains a important data for
RealPlayer it is
possible to cause future security problems because of its overwrite with
marked by attacker.


Successful exploitation may allow the attacker to run arbitrary code in
context of user running Real*Player*.


Due to severity of this bug i will not publish any poc codes.

best regards,

Piotr Bania - <bania.piotr () gmail com> - 0xCD, 0x19
Fingerprint: 413E 51C7 912E 3D4E A62A  BFA4 1FF6 689F BE43 AC33
http://www.piotrbania.com  - Key ID: 0xBE43AC33

              - "The more I learn about men, the more I love dogs."

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