CIS CYBER SECURITY ADVISORIES
MS-ISAC CYBER SECURITY ADVISORY NUMBER:
Cumulative Security Update for Internet Explorer (MS11-057) - RISK: HIGH
Multiple vulnerabilities have been discovered in Microsoft's web browser, Internet Explorer, which could allow an attacker to take complete control of an affected system. Successful exploitation of these vulnerabilities could result in anattacker gaining the same privileges as the logged on user. Depending on theprivileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.Several of the vulnerabilities can also lead to information disclosure if successfully exploited.
- Internet Explorer 6
- Internet Explorer 7
- Internet Explorer 8
- Internet Explorer 9
- Large and medium government entities: High
- Small government entities: High
- Large and medium business entities: High
- Small business entities: High
Home users: High
Seven vulnerabilities have been discovered in Microsoft Internet Explorer. Details of these vulnerabilities are as follows:
Remote Code Execution Vulnerabilities
Four remote code execution vulnerabilities have been discovered in Internet Explorer. Three of these vulnerabilities are memory corruption vulnerabilities that occur due to the way Internet Explorer accesses objects in memory that have not been properly initialized, deleted, or corrupted due to a race condition. An additional vulnerability could allow an attacker to use Internet Explorer in order to invoke the telnet URI handler in such a way that would allow remote code to run on the user's machine. These vulnerabilities may be exploited if a user visits a web page that is specifically crafted to take advantage of the vulnerabilities. Successful exploitation of any of these vulnerabilities could result in an attacker taking complete control of the system.
Information Disclosure Vulnerabilities
Three information disclosure vulnerabilities have also been discovered in Internet Explorer. An attacker could successfully exploit the first vulnerability byconvincing a user to visit a specially crafted website and perform a drag and drop operation on the page. This could allow the attacker to view cookie files stored on the local machine. The second and third vulnerabilities can be exploited by convincing a user to visit a specially crafted website,which would allow an attacker to access information in other domains or Internet Explorer Zones.
We recommend the following actions be taken:
- Apply appropriate patches provided by Microsoft to vulnerable systems immediatelyafter appropriate testing.
- Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
- Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.