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# AVAST Universal Core Installer Multiple Vulnerabilities

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Title:
======
AVAST Universal Core Installer - Multiple Vulnerabilities


Date:
=====
2013-06-28


References:
===========
http://www.vulnerability-lab.com/get_content.php?id=966


VL-ID:
=====
965


Common Vulnerability Scoring System:
====================================
4.2


Introduction:
=============
Avast! (styled avast!) is - both freeware and payable - an antivirus computer program with user interface that includes

41 languages, available to Microsoft Windows, Mac OS X and Linux users. The name Avast is an acronym of `Anti-Virus
– Advanced Set`.
The official, and current logo of Avast! is a white orb with the letter `a` on it and an orange circle around it,
sticking out to
four directions.Its developer, AVAST Software a.s. (formerly known as ALWIL Software a.s.), has headquartered in Prague,
Czech
Republic, with offices in Linz, Austria; Friedrichshafen, Germany; and San Mateo, California.

It has been awarded VB100 Award by Virus Bulletin multiple times for 100% detection of `in-the-wild` viruses, and also
won the Secure Computing Readers`Trust Award. The central scanning engine has been certified by ICSA Labs and West Coast
Labs`
Checkmark process.Avast! competes in the antivirus industry against Avira, AVG Technologies, Bitdefender, F-Secure,
Frisk, Kaspersky,
McAfee, Symantec and Trend Micro among others.

(Copy of the Homepage: http://en.wikipedia.org/wiki/Avast! )


Abstract:
=========
The Vulnerability Laboratory Research Team discovered a persistent code injection and local command path injection
vulnerability in the AVAST Universal Core Installer application software.


Report-Timeline:
================
2013-06-06: Researcher Notification & Coordination (Ateeq Khan)
2013-06-07: Vendor Notification (AVAST! - Security Incident Team)
2013-06-09: Vendor Response/Feedback (AVAST! - Security Incident Team)
2013-**-**: Vendor Fix/Patch (AVAST! - Developer Team)
2013-06-28: Public Disclosure (Vulnerability Laboratory)


Status:
========
Published


Exploitation-Technique:
=======================
Local


Severity:
=========
Medium


Details:
========
It has been discovered that the Core avast installer application is vulnerable to persistent code injection and local
command path injection vulnerability. During the testing, I was able to succesfully read/load and execute any
file/application
from local system having the local admin priviledges which makes this bug alot more interesting.

Initially the bug was an HTML code injection flaw only however, with more indepth analysis, it was revealed that the
severity of this vulnerability is far more differnt. A simple <a href> tag bypasses the AVAST Sandbox and drops a
locall CMD
shell on the system where AVAST is installed. You can technically access any file / application, execute it. It seems
like We
can control explorer.exe and through that we are even able to browse local folders and access any file, we can even
browse external
websites.

The bug exists in the Custom Install Section under Destination Field. Since proper input sanatization is not being
performed, a user can insert any HTML code which then gets executed successfully. For a POC i used the <img> and
<a href> tags to
read/load and execute files from my local system. I believe there may be possibilities of multiple attack vectors
keeping in mind
the scope
of this vulnerability.

During the POC, I was able to successfully bypass the AVAST sandbox and I was able to run local system level commands
using the AVAST Interface.

These sort of vulnerabilities can result in multiple attack vectors on the clients end which may eventually result in
complete compromise of
the end user system.

Exploitation of this vulnerability requires a low or medium user interaction. Successful exploitation of the
vulnerability may result
in malicious script code being executed resulting in local command/shell injection, persistent phishing, Client side
redirects and
similar dangerous attacks.

Vulnerable Product(s):
[+] avast Premier Antivirus Installer - Latest Release
[+] avast Antivirus Pro Installer - Latest Release
[+] avast Free Antivirus Installer Version 8 - Latest Release
[+] avast Internet Security Suite Installer - Latest Release

Vulnerable Module(s):
[+] Custom Install

Vulnerable Field(s):
[+] Enter the Destination Directory


Proof of Concept:
=================
The vulnerabilities can be exploited by local attackers with low system privilege account and low user interaction.
For demonstration or reproduce ...

a) Run the avast Premier Installer binary file (avast_premier_antivirus_setup.exe)
b) Click on Custom Install
c) under the field "Enter the Destination directory" enter the following Payload

C:Program FilesAVAST SoftwareAvast<h1>Vulnerable<a href="cmd">ClickME

d) Click Next twice untill you reach the "Installation Information" Window
e) Scroll down and you should be able to see our Injected Payload.
f) If you click on "ClickME" you should get a CMD shell spawned on the local system hence proving the
existence of this
vulnerability.
g If you proceed with the installation and continue, the installation will fail eventually and once again in the Final

Install Log you
will see the executed payload.

Note: All tests were performed on a system running latest version of MicroSoft Windows 7 OS.


Solution:
=========
By default, no user should be allowed to inject HTML code in the application.
This can be mitigated by performing proper input sanatization of the vulnerable fields.

All illegal characters should also be escaped and application source code should be hardened overall.
Proper input encoding and format parse in the source code will fix this issue.


Risk:
=====
The security risk of these kinds of vulnerabilities are estimated as medium(+).


Credits:
========
Vulnerability Laboratory [Research Team] - Ateeq Khan [ateeq () evolution-sec com]


Disclaimer:
===========
The information provided in this advisory is provided as it is without any warranty. Vulnerability-Lab disclaims all
warranties,
either expressed or implied, including the warranties of merchantability and capability for a particular purpose.
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damages. Some
states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing
limitation
may not apply. We do not approve or encourage anybody to break any vendor licenses, policies, deface websites, hack
into databases
or trade with fraud/stolen material.

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Copyright &#169; 2013 | Vulnerability Laboratory



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# Iranian Exploit DataBase = http://IeDb.Ir [2013-07-05]

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