Title:
======
FlashFXP v4.1.8.1701 - Buffer Overflow Vulnerability
Introduction:
=============
FlashFXP is a FTP (File Transfer Protocol) client for Windows, it offers you easy and fast ways to transfer any file between other local
computers (LAN - Local Area Network) running a FTP server or via the Internet (WAN - Wide Area Network) and even directly between two
servers using Site to Site transfers (FXP - File eXchange Protocol). Use FlashFXP to publish and maintain your website, Upload and download
documents, photos, videos, music and more! Share your files with your friends and co-workers using the powerful site manager. There are many
features and advanced options available within FlashFXP which are being added with the release of each new version stable or beta*. The software
is available in over 20 languages and under active development. FlashFXP offers high security, performance, and reliability that you can always
depend on to get your job done swiftly and efficiently.
(Copy of the Vendor Homepage: http://www.flashfxp.com)
Report-Timeline:
================
2012-02-27: Vendor Notification
2012-02-28: Vendor Response/Feedback
2012-03-01: Public or Non-Public Disclosure
Details:
========
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 Lösung für das Problem suchen.
UI[5]=Online nach einer Lösung suchen und das Programm schließen
UI[6]=Später online nach einer Lösung suchen und das Programm schließen
UI[7]=Programm schließen
...
FriendlyEventName=Nicht mehr funktionsfähig
ConsentKey=BEX
AppName=FlashFXP
AppPath=C:\Program Files (x86)\FlashFXP 4\FlashFXP.exe
