FlashFXP v4.1.8.1701 - Buffer Overflow Vulnerability

2012-03-1900:00:00

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Title:

Date:

2012-03-01

References:

http://www.vulnerability-lab.com/get_content.php?id=462

VL-ID:

462

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)

Abstract:

The Vulnerability Laboratory Research Team discovered a Buffer Overflow Vulnerability on FlashFXP v4.1.8.1701.

Report-Timeline:

2012-02-27: Vendor Notification
2012-02-28: Vendor Response/Feedback
2012-03-01: Public or Non-Public Disclosure

Status:

Published

Affected Products:

OpenSight Software
Product: FlashFXP Software Client v4.1.8.1701

Exploitation-Technique:

Local

Severity:

High

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]

Picture(s):
…/1.png
…/2.png
…/3.png
…/4.png
…/5.png

Proof of Concept:

The vulnerability can be exploited by local & remote attackers. For demonstration or reproduce …

Manually reproduce …

Download & open the software client
Connect to a random server for inter action
Enable the Option Settings => Filters => Skip-List
Open the Option => Filter Settings
Add a new (Skip-List)one by Including a large unicode string & wait for the exception-handling
The exception-handling out of bounds comes up
You pass it 2 times by clicking continue …
The software is now crashing with a stable bex exception & displays input as offset[6]
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 Losung fur das Problem suchen.
UI[5]=Online nach einer Losung suchen und das Programm schlie?en
UI[6]=Spater online nach einer Losung suchen und das Programm schlie?en
UI[7]=Programm schlie?en
…
FriendlyEventName=Nicht mehr funktionsfahig
ConsentKey=BEX
AppName=FlashFXP
AppPath=C:\Program Files (x86)\FlashFXP 4\FlashFXP.exe

Reference(s):
…/AppCrash_FlashFXP.exe_cb63a668207dbeae0f33144dffb1e66eae843_0a310ac0
…/AppCrash_FlashFXP.exe_cb63a668207dbeae0f33144dffb1e66eae843_07c4b531
…/bugreport1.txt
…/bugreport2.txt
…/video-poc-demo.wmv

Risk:

The security risk of the buffer overflow vulnerability is estimated as high(-).

Credits:

Vulnerability Research Laboratory - Benjamin Kunz Mejri

Disclaimer:

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either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-
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                                            Copyright © 2012|Vulnerability-Lab

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