Microsoft’s September Tuesday update has 12 security bulletins to address 55 vulnerabilities, including one Office graphics image bug that has reportedly been used in limited targeted attacks on customers.
Microsoft has rated five of the 12 bulletins for September as critical, which address remote code execution bugs in its Edge browser, Internet Explorer, Windows Journal, Office and Graphics Components.
The remaining seven bulletins are rated important and address flaws in Active Directory, Windows Media Center, .NET, Windows Task Manage, Exchange Server, Skype for Business Server and Lync Server, and Hyper-V.
Perhaps one of the most urgent vulnerabilities that customers will need to fix is an Office bug with the designated identifier CVE-2015-2545 under bulletin MS15-099.
Microsoft said the remote code execution bug, dubbed Office Malformed EPS File Vulnerability, can be exploited when a user opens an Office file containing a malformed graphics image. The flaw is reportedly already being used to attack customers.
“When this security bulletin was issued, Microsoft had received reports of limited targeted attacks using this vulnerability,” Microsoft said.
The bug was reported to Microsoft by security firm FireEye under coordinated disclosure.
A likely attack scenario for this bug is that an attacker will send a malicious Word document in an email to targets due to Word being the default email reader in Outlook.
"If Microsoft Word is the selected email reader, which is the default setting, then an attacker could leverage Outlook for an email-based attack by sending a specially crafted file, containing an EPS image binary, to the targeted user," said Microsoft.
"In this scenario this attack vector requires minimal user action (as in viewing a specially crafted email through the preview pane in Outlook) to be exploited.”
Alternatively an attacker could host a malicious Word file on a website, however that would require them to first convince a target to visit the site and then dupe them into opening the malicious file.
Microsoft noted that attackers could not exploit the bug automatically via a web-based attack.
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