Microsoft Fixes Two Security Flaws in Outlook

A critical memory corruption vulnerability in Microsoft Outlook that can be exploited via the Preview Pane feature of the email program was fixed today amid a flurry of patches in Microsoft's February Patch Tuesday security update.

The Outlook flaw (CVE-2018-0852) could be exploited by an attacker to execute malicious code remotely, and if the victim user operates with administrative user rights, the attacker could wrest control of the entire system, Microsoft said in the security update.

Microsoft this month overall has issued patches for some 50 vulnerabilities, including 14 flagged as critical.

Dustin Childs, communications manager for Trend Micro's ZDI team, says the Outlook flaw should be a priority, especially since merely viewing a malicious email in the Preview Pane could allow the attack to execute. "Even more than the publicly known bugs, this CVE falls into the “Patch Now!” category," Childs wrote in a blog post today. "The end user targeted by such an attack doesn't need to open or click on anything in the email – just view it in the Preview Pane. If this bug turns into active exploits – and with this attack vector, exploit writers will certainly try – unpatched systems will definitely suffer."

Microsoft also patched a second Outlook flaw, an elevation of privilege bug, that (CVE-2018-0850) tied to Outlook's processing of incoming messages. It doesn't properly validate the email format, so an attacker could use that flaw to "load a local or remote message store" via SMB, according to Microsoft. An attacker would have to send a malicious email to the victim to initiate the attack.

"Outlook attempts to open the pre-configured message on receipt of the email. You read that right – not viewing, not previewing, but upon receipt. That means there’s a potential for an attacker to exploit this merely by sending an email," ZDI's Childs said. 

Also among the patches in this month's Patch Tuesday were updates to Internet Explorer, Microsoft Edge, Windows, MChakraCore, and Adobe Flash.

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