Title:

AVAST Internet Security Suite - Persistent Vulnerabilities

Date:

2013-06-27

References:

http://www.vulnerability-lab.com/get_content.php?id=969

VL-ID:

969

Common Vulnerability Scoring System:

3.4

Introduction:

AVAST Software (www.avast.com), maker of the world’s most popular antivirus, protects over 184 million computers
and mobile devices with our security applications. In business for over 25 years, AVAST is one of the oldest
companies in the computer security business, with a portfolio covering everything from free antivirus for PC, Mac,
and Android, to premium suites and services for business. In addition to being top-ranked by consumers on popular
download portals worldwide, AVAST performance is certified by, among others, VB100, AV-Comparatives,
AV-Test, OPSWAT, ICSA Labs, and West Coast Labs.

Vendor Homepage: http://www.avast.com/
Product website: http://www.avast.com/internet-security

Abstract:

The Vulnerability Labs Team has discovered a persistent code injection & local command path injection vulnerability in the AVAST Internet Security Suite.

Report-Timeline:

2013-06-09: Researcher Notification & Coordination (Ateeq Khan)
2013-06-11: Vendor Notification (AVAST - Security Incident Team)
2013-06-15: Vendor Response/Feedback (AVAST - Security Incident Team)
2013--: Vendor Fix/Patch (AVAST - Developer Team)
2013-06-27: Public Disclosure (Vulnerability Laboratory)

Status:

Published

Affected Products:

AVAST!
Product: Internet Security Suite Software 8.0.1489

Exploitation-Technique:

Local

Severity:

Medium

Details:

It has been discovered that the avast Internet Security Suite is vulnerable to persistent code injection and local command path injection vulnerability.
During the testing, I was able to successfully read/load and execute any file/application from local system having the local admin privileges.

Initially the bug was an HTML code injection flaw only however, with more deep analysis, it was revealed that the severity of
this vulnerability is far more differnet. 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 Firewall Module under the Network Utilities Section. 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.

Proper user input sanatization of the source code should be performed because these sort of basic security controls should
always be intact to meet all regulatory and compliance standards.

Vulnerable Product(s):
[+] Avast Internet Security Suite Installer - Latest Release

Vulnerable Module(s):
[+] Firewall

Vulnerable Section(s):
[+] Network Utilities

Vulnerable Field(s)
[+] IP Address Details
[+] Graphical Traceroute

Proof of Concept:

Proof of Concept #1

For reproducing the bug, please follow the below mentioned steps:

a) Open the avast internet security suite, goto Firewall and Click on Network Utilities
b) Enter the following payload under the IP ADDRESS DETAILS

<h1>Vulnerable</h1> or <iframe src=test.de>

c) Click on "Get Details" and you should be able to see a popup within a few seconds proving the existence of this vulnerability.
d) To spawn a Command Shell on the local system, use the payload "><a href="cmd">CLICKME
e) On the next avast information popup box that appears, click anywhere and you should be able to spawn a local CMD shell.

Proof of Concept #2

For reproducing the bug, please follow the below mentioned steps:

a) Open the avast internet security suite, goto Firewall and Click on Network Utilities
b) Enter the following payload under the "Graphical Trace-Route" section

<h1>Vulnerable</h1> or <iframe src=test.de>

c) Click on "Get Details" and you should be able to see a popup within a few seconds proving the existence of this vulnerability.
d) To spawn a Command Shell on the local system, use the payload "><a href="cmd">CLICKME
e) On the next avast information popup box that appears, click anywhere and you should be able to spawn a local CMD shell.

POC Technical Description & Fix:

Here, we used the common HTML tags as our payload. The fact that user injected HTML code is being executed successfully raises
concerns for this core applications security. Then, the fact that using just the <a href> tag, we can easily bypass AVAST Sandbox
and gain local system shell with privileges of the user that installed the application initially which in most cases will be administrator
is very critical. I believe this bug can be further escalated to gain more interested results.

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 sanatization 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 ([email protected])

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