PT-2013-72: 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/

Threatscape