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Vulnerability in Microsoft Office for Mac Could Allow for Remote Code Execution

MS-ISAC ADVISORY NUMBER:

2019-119

DATE(S) ISSUED:

11/04/2019

OVERVIEW:

A vulnerability has been discovered in Microsoft Office for Mac, which could allow for remote code execution. Microsoft Office for Mac is an office productivity software. Successful exploitation of this vulnerability 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 with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

THREAT INTELLIGENCE:

There is currently no report of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

  • Microsoft Office 2011 for Mac

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: MEDIUM
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: MEDIUM
Home Users:
LOW

TECHNICAL SUMMARY:

A vulnerability has been discovered in Microsoft Office for Mac, which could allow for remote code execution. In an email attack scenario, an attacker could exploit these vulnerabilities by sending a specially crafted file to a user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file designed to exploit this vulnerability. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file.

Successful exploitation of this vulnerability could result in the attacker gaining control of the affected system. Depending on the privileges associated with this application, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. If this application has been configured to have fewer user rights on the system, exploitation of the most severe of these vulnerabilities could have less impact than if it was configured with administrative rights.

RECOMMENDATIONS:

We recommend the following actions be taken:

  • Block SYLK files over web and email gateways.
  • Block SYLK files in Microsoft Office 2011 for Mac.
  • Enable the security setting "Disable all macros with notification".
  • Since Microsoft Office 2011 for Mac is end of life, update to a supported version immediately after appropriate testing because no patch is available for the 2011 version.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Remind users not to visit un-trusted websites or open attachments provided by unknown or un-trusted sources.
  • Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

REFERENCES:

CMU – Software Engineering Institute::
https://kb.cert.org/vuls/id/125336/

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