CIS CYBER SECURITY ADVISORIES

MS-ISAC CYBER SECURITY ADVISORY NUMBER:
2011-036

DATE(S) ISSUED:
06/14/2011

SUBJECT:
Cumulative Security Update for Internet Explorer (MS11-050)

OVERVIEW:

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 an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts withfull user rights. Several of the vulnerabilities can also lead to information disclosure if successfully exploited.

SYSTEMS AFFECTED:

  • Internet Explorer 6
  • Internet Explorer 7
  • Internet Explorer 8
  • Internet Explorer 9

RISK:
Government:

  • Large and medium government entities: High
  • Small government entities: High

Businesses:

  • Large and medium business entities: High
  • Small business entities: High

Home users: High

DESCRIPTION:
Eleven vulnerabilities have been discovered in Microsoft Internet Explorer. Details of these vulnerabilities are as follows:

Memory Corruption Vulnerabilities
Eight remote code execution vulnerabilities exist in the way Internet Explorer accesses objects in memory that have not been properly initialized or deleted. These vulnerabilities may be exploited if a user visits a web page that is specifically crafted to take advantage of the vulnerabilities. An alternative attack vector is possible if an attacker could embed an ActiveX control that is marked 'safe for initialization' in an application or Microsoft Office document that hosts the IE rendering engine. Successful exploitation of any of these vulnerabilities could result in an attacker gaining the same privileges as the logged on user. Depending on the privileges associated with the user, an attacker could then install programs; view, change, or delete data; or create new accounts withfull user rights.

Information Disclosure Vulnerabilities
Three information disclosure vulnerabilities have also been discovered in Internet Explorer. An attacker who successfully exploited any of these vulnerabilities, by convincing a user to visit a specially crafted website, could potentially access information in other domains or Internet Explorer Zones.

RECOMMENDATIONS:
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, IM (Instant Messages) or attachments especially from un-trusted sources.

REFERENCES:
Microsoft:
http://www.microsoft.com/technet/security/bulletin/ms11-050.mspx

CVE:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1246
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1250
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1251
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1252
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1254
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1255
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1256
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1258
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1260
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1261
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1262

SecurityFocus:
http://www.securityfocus.com/bid/48199
http://www.securityfocus.com/bid/48200
http://www.securityfocus.com/bid/48201
http://www.securityfocus.com/bid/48202
http://www.securityfocus.com/bid/48203
http://www.securityfocus.com/bid/48204
http://www.securityfocus.com/bid/48205