Overview
The AVG Secure Search toolbar, also known as AVG Safeguard includes an ActiveX control that provides a number of unsafe methods, which may allow a remote, unauthenticated attacker to execute arbitrary code with the privileges of the user.
Description
AVG Secure Search is a toolbar add-on for web browsers that "... provides an additional security layer while searching and surfing to protect you from infected websites." One of the components provided by AVG Secure Search is an ActiveX control called ScriptHelperApi, which is provided by ScriptHelper.exe. This ActiveX control is marked as Safe for Scripting in Internet Explorer, which means that the author has determined that the control cannot be repurposed by an attacker. Because this control does not internally enforce any restrictions on which sites may invoke its methods, such as by using the SiteLock template, this means that any website can invoke the methods exposed by the ScriptHelper ActiveX control. The installer for AVG Secure Search also sets the ElevationPolicy registry value for the control, which means that the control is excluded from the Internet Explorer Protected Mode sandbox. The installer for AVG Secure Search also sets the Preapproved registry value, which bypasses the Internet Explorer ActiveX Opt-In feature that was introduced with IE 7. The AVG Safeguard and Secure Search ScriptHelper ActiveX control versions up to and including version 18.1.6 contain a number of unsafe methods that can be used in Internet Explorer. Other browsers do not appear to be affected. |
Impact
By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), an attacker may be able to download and execute arbitrary code with the privileges of the logged-on user. |
Solution
Apply an update |
Disable the AVG ScriptHelper ActiveX control in Internet Explorer
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{F25AF245-4A81-40DC-92F9-E9021F207706}] "Compatibility Flags"=dword:00000400 [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\ActiveX Compatibility\{F25AF245-4A81-40DC-92F9-E9021F207706}] "Compatibility Flags"=dword:00000400 |
Vendor Information
CVSS Metrics
| Group | Score | Vector |
|---|---|---|
| Base | 9.3 | AV:N/AC:M/Au:N/C:C/I:C/A:C |
| Temporal | 8 | E:POC/RL:W/RC:C |
| Environmental | 6.0 | CDP:ND/TD:M/CR:ND/IR:ND/AR:ND |
References
- http://www.avg.com/us-en/secure-search
- http://msdn.microsoft.com/en-us/library/aa751977%28v=vs.85%29.aspx
- http://msdn.microsoft.com/en-us/library/aa752035%28v=vs.85%29.aspx#ax_repurposing
- http://msdn.microsoft.com/en-us/library/aa752035%28v=vs.85%29.aspx#ax_judging
- http://msdn.microsoft.com/en-us/library/bb250462%28v=vs.85%29.aspx
- http://windows.microsoft.com/en-us/windows-vista/what-does-internet-explorer-protected-mode-do
- http://blogs.msdn.com/b/ieinternals/archive/2011/04/02/activex-control-restrictions-in-ie.aspx
- http://msdn.microsoft.com/en-us/library/bb250471%28v=vs.85%29.aspx
Acknowledgements
This vulnerability was reported by Will Dormann of the CERT/CC.
This document was written by Will Dormann.
Other Information
| CVE IDs: | CVE-2014-2956 |
| Date Public: | 2014-07-07 |
| Date First Published: | 2014-07-07 |
| Date Last Updated: | 2014-07-25 14:04 UTC |
| Document Revision: | 25 |