(PT-2013-72) Positive Technologies Security Advisory
XML External Entities Resolution vulnerability in Microsoft Office Excel

Vulnerable software

Microsoft Office Excel
Version: 2010 SP2 and earlier; 2007 SP3 and earlier; 2003 SP3 and earlier

Microsoft Excel Viewer
Version: 2007 SP3 and earlier

Link:
http://microsoft.com/

Severity level

Severity level: Medium
Impact: Internal Network Resources and File System Access, Denial of Service 
Access Vector: Remote

CVSS v2:
Base Score: 5.8
Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:P)

CVE: CVE-2013-3159

Software description

Microsoft Office Excel is a commercial spreadsheet application written and distributed by Microsoft for Microsoft Windows and Mac OS X.

Vulnerability description

The specialists of the Positive Research center have detected an XML External Entities Resolution vulnerability in Microsoft Office Excel.

The vulnerability is possible due to unsafe parsing of XML external entities. If an attacker makes a victim open a specially crafted XML document, Microsoft Office Excel installed on the vistim's system will automatically send the contents of local or remote resource to the attacker's server. It also makes possible to conduct denial of service attacks.

How to fix

Use vendor's advisory:
http://technet.microsoft.com/en-us/security/bulletin/ms13-073

Advisory status

26.11.2012 - Vendor gets vulnerability details
10.09.2013 - Vendor releases fixed version and details 
09.10.2013 - Public disclosure

Credits

The vulnerability was detected by Timur Yunusov, Alexey Osipov and Ilya Karpov, Positive Research Center (Positive Technologies Company)

References

http://en.securitylab.ru/lab/PT-2013-72

Reports on the vulnerabilities previously discovered by Positive Research:

http://www.ptsecurity.com/research/advisory/
http://en.securitylab.ru/lab/

About Positive Technologies

Positive Technologies www.ptsecurity.com is among the key players in the IT security market in Russia.

The principal activities of the company include the development of integrated tools for information security monitoring (MaxPatrol); providing IT security consulting services and technical support; development of the Securitylab leading Russian information security portal.

Among the clients of Positive Technologies, there are more than 40 state enterprises, more than 50 banks and financial organizations, 20 telecommunication companies, more than 40 plant facilities, as well as IT, service and retail companies from Russia, the CIS countries, the Baltic States, China, Ecuador, Germany, Great Britain, Holland, Iran, Israel, Japan, Mexico, the Republic of South Africa, Thailand, Turkey, and the USA.

Positive Technologies is a team of highly skilled developers, advisers and experts with years of vast hands-on experience. The company specialists possess professional titles and certificates; they are the members of various international societies and are actively involved in the IT security field development.