Flash Uninitialized Stack Variable MPD Parsing Memory Corruption

Source: https://code.google.com/p/google-security-research/issues/detail?id=316&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id
 
[Tracking for: https://code.google.com/p/chromium/issues/detail?id=472201]
 
Credit is to bilou, working with the Chromium Vulnerability Rewards Program.
 
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VULNERABILITY DETAILS
Loading a weird MPD file can corrupt flash player's memory.
 
VERSION
Chrome version 41.0.2272.101, Flash 17.0.0.134
Operating System: Win 7 x64 SP1
 
REPRODUCTION CASE
I'm ripping most of this from scarybeasts' sources. I'm sure he's ok with that =D.
 
"To reproduce, host the attached SWF and other files on a web server (e.g. localhost) and load it like this:"
 
"http://localhost/PlayManifest.swf?file=gen.mpd
 
"To compile the .as file, I had to use special flags to flex:"
 
"mxmlc -target-player 14.0 -swf-version 25 -static-link-runtime-shared-libraries ./PlayManifest.as"
"(This also requires that you have v14.0 of playerglobals.swc installed. Any newer version should also be fine.)"
 
 
On Win7 x64 sp1 with Chrome 32 bit, crash like this:
6AA8B67C | 8B C3                    | mov eax,ebx                             |
6AA8B67E | E8 A1 05 00 00           | call pepflashplayer.6AA8BC24            |
6AA8B683 | EB A8                    | jmp pepflashplayer.6AA8B62D             |
6AA8B685 | 89 88 D0 00 00 00        | mov dword ptr ds:[eax+D0],ecx           |  // crash here, eax points somewhere in pepflashplayer.dll
6AA8B68B | 8B 88 88 00 00 00        | mov ecx,dword ptr ds:[eax+88]           |
6AA8B691 | 33 D2                    | xor edx,edx                             |
6AA8B693 | 3B CA                    | cmp ecx,edx                             |
6AA8B695 | 74 07                    | je pepflashplayer.6AA8B69E              |
6AA8B697 | 39 11                    | cmp dword ptr ds:[ecx],edx              |
6AA8B699 | 0F 95 C1                 | setne cl                                |
 
 
At first sight this looks to be an uninitialized stack variable but I might be wrong.
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Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/37845.zip

#  0day.today [2018-01-26]  #