A Buffer Overflow Vulnerability is detected on FlashFXPs Software Client v4.1.8.1701. The vulnerability is located when processing to force a ListIndex Out of Bound(s) exception which allows to overwrite ecx & eip of the affected software process. Successful exploitation can result in process compromise, execution of arbitrary code, system compromise or escaltions with privileges of affected vulnerable software process.
The flaw is a direct result of a fixed length buffer being used in the TListBox control and the lack of range checking. The code assumes that the string returned by the listbox control will be less than 4097 characters. It uses a fixed size buffer of 4096 bytes and any text longer than this will overflow and overwrite the memory beyond it. The TComboBox control also suffers a similar flaw.
Vulnerable Module(s):
[+] List Index & Exception Handling [TListBox]
Proof of Concept:
The vulnerability can be exploited by local & remote attackers. For demonstration or reproduce ...
Manually reproduce ...
1. Download & open the software client
2. Connect to a random server for inter action
3. Enable the Option Settings => Filters => Skip-List
3. Open the Option => Filter Settings
4. Add a new (Skip-List)one by Including a large unicode string & wait for the exception-handling
5. The exception-handling out of bounds comes up
6. You pass it 2 times by clicking continue ...
7. The software is now crashing with a stable bex exception & displays input as offset[6]
8. Now you can overwrite the ecx & eip of the affected vulnerable software process to exploit the client system
Note: To exploit the bug (remote) an attacker needs to know the included filters of the connected client to send large strings.
--- Exception Error #1 ---
date/time : 2012-02-28, 16:38:58, 531ms
computer name : HOSTBUSTER
user name : Rem0ve
operating system : Windows 7 Tablet PC x64 Service Pack 1 build 7601
system language : German
system up time : 5 days 13 hours
program up time : 7 minutes 2 seconds
processors : 2x Intel(R) Core(TM)2 Duo CPU T6600 @ 2.20GHz
physical memory : 2243/4091 MB (free/total)
free disk space : (C:) 207,54 GB
display mode : 1366x768, 32 bit
process id : $16fc
allocated memory : 50,75 MB
executable : FlashFXP.exe
exec. date/time : 2012-01-15 22:45
executable hash : 34A53BD60479975EA6DAAB55B8D878B4
version : 4.1.8.1701
ANSI code page : 1252
callstack crc : $1083d124, $c40af1d7, $90cfaf70
exception number : 1
exception class : EStringListError
exception message : List index out of bounds (0).
--- Exception Error #2 ---
date/time : 2012-02-28, 16:39:57, 530ms
computer name : HOSTBUSTER
user name : Rem0ve
operating system : Windows 7 Tablet PC x64 Service Pack 1 build 7601
system language : German
system up time : 5 days 13 hours
program up time : 8 minutes
processors : 2x Intel(R) Core(TM)2 Duo CPU T6600 @ 2.20GHz
physical memory : 2220/4091 MB (free/total)
free disk space : (C:) 207,54 GB
display mode : 1366x768, 32 bit
process id : $16fc
allocated memory : 66,67 MB
executable : FlashFXP.exe
exec. date/time : 2012-01-15 22:45
executable hash : 34A53BD60479975EA6DAAB55B8D878B4
version : 4.1.8.1701
ANSI code page : 1252
callstack crc : $b94d6925, $57f8c46d, $8f2c6734
exception number : 2
exception class : EStringListError
exception message : List index out of bounds (0).
--- Exception BEX #3 (Overwrite) ---
Version=1
EventType=BEX
EventTime=129749175156198070
ReportType=2
Consent=1
ReportIdentifier=34b76897-6223-11e1-afbd-c4a714168486
IntegratorReportIdentifier=34b76896-6223-11e1-afbd-c4a714168486
WOW64=1
Response.type=4
Sig[0].Name=Anwendungsname
Sig[0].Value=FlashFXP.exe
Sig[1].Name=Anwendungsversion
Sig[1].Value=4.1.8.1701
Sig[2].Name=Anwendungszeitstempel
Sig[2].Value=2a425e19
Sig[3].Name=Fehlermodulname
Sig[3].Value=StackHash_e98d
Sig[4].Name=Fehlermodulversion
Sig[4].Value=0.0.0.0
Sig[5].Name=Fehlermodulzeitstempel
Sig[5].Value=00000000
Sig[6].Name=Ausnahmeoffset
Sig[6].Value=41414141 <= ECX | EIP
Sig[7].Name=Ausnahmecode
Sig[7].Value=c0000005
Sig[8].Name=Ausnahmedaten
Sig[8].Value=00000008
DynamicSig[1].Name=Betriebsystemversion
DynamicSig[1].Value=6.1.7601.2.1.0.768.3
DynamicSig[2].Name=Gebietsschema-ID
DynamicSig[2].Value=1031
DynamicSig[22].Name=Zusatzinformation 1
DynamicSig[22].Value=e98d
DynamicSig[23].Name=Zusatzinformation 2
DynamicSig[23].Value=e98dfca8bcf81bc1740adb135579ad53
DynamicSig[24].Name=Zusatzinformation 3
DynamicSig[24].Value=6eab
DynamicSig[25].Name=Zusatzinformation 4
DynamicSig[25].Value=6eabdd9e0dc94904be3b39a1c0583635
UI[2]=C:\Program Files (x86)\FlashFXP 4\FlashFXP.exe
UI[3]=FlashFXP funktioniert nicht mehr
UI[4]=Windows kann online nach einer L sung f r das Problem suchen.
UI[5]=Online nach einer L sung suchen und das Programm schlie en
UI[6]=Sp ter online nach einer L sung suchen und das Programm schlie en
UI[7]=Programm schlie en
...
FriendlyEventName=Nicht mehr funktionsf hig
ConsentKey=BEX
AppName=FlashFXP
AppPath=C:\Program Files (x86)\FlashFXP 4\FlashFXP.exe
