Microsoft Fixes 129 Vulnerabilities for September's Patch Tuesday

Microsoft today released patches for 129 CVEs (common vulnerabilities and exposures) as part of its monthly Patch Tuesday rollout. This marks seven consecutive months of 110+ bugs fixed and brings the yearly total close to 1,000.

September's Patch Tuesday addressed vulnerabilities in Microsoft Windows, the Edge browser, ChakraCore, Internet Explorer, SQL Server, Office and Office Services and Web Apps, Microsoft Dynamics, Visual Studio, Exchange Server, ASP.NET, OneDrive, and Azure DevOps. Of the 129 bugs fixed, 23 are classified as critical, 105 are important, and one ae moderate in severity.

None of the flaws patched today were publicly known or under active attack; however, there are a few that stand out due to their severity. One of these is Microsoft Exchange memory corruption vulnerability CVE-2020-16875, a critical flaw that could be exploited by sending a malicious email containing exploit code to a vulnerable Exchange server. If successful, an attacker could then install programs; view, edit, or delete data; or create new user accounts.

"We have seen the previously patched Exchange bug CVE-2020-0688 used in the wild, and that requires authentication," writes Dustin Childs of Trend Micro's Zero-Day Initiative in a blog post. "We'll likely see this one in the wild soon. This should be your top priority."

Today brought fixes for seven critical remote code execution vulnerabilities in SharePoint 2010 through 2019. Five of these (CVE-2020-1200, CVE-2020-1210, CVE-2020-1452, CVE-2020-1453, and CVE-2020-1576) exist in how SharePoint fails to check the source markup of an application loaded to the server, and exploitation could let an attacker run malicious code on the server. Given SharePoint is often installed on large business networks, these patches are important.

Microsoft has addressed a couple of critical remote code execution bugs in Windows Codecs Library. Both of these could be exploited by crafting a malicious image file and having any program process the malicious image, explains Chris Hass, director of information security and research at Automox. If successful, they could obtain data to further compromise the system.

"With the number of images being shared constantly on Slack, Zoom, or email, this vulnerability could prove enticing for attackers to leverage," Hass explains. Today's updates addresses CVE-2020-1129 and CVE-2020-1319 by correcting how Codecs Library handles objects in memory. 

Hass also points to CVE-2020-0878, a memory corruption bug in Microsoft browsers, as an issue to patch. The flaw exists in the way Microsoft browsers access objects in memory and affects versions of Microsoft Edge and Internet Explorer. An attacker could host a specially crafted site designed to exploit the flaw and convince a user to view it, or they could take advantage of compromised websites, or submit crafted content to sites that host user-provided content.

However, the vulnerability cannot be exploited by simply viewing the malicious content. An attacker must convince users to take action, whether through an email or instant message, to get them to open an attachment. If the user is logged in with administrative rights, a successful attacker could take control of an affected system.

"Although there have been many memory corruption RCE vulnerabilities disclosed this month, Microsoft currently has around 13% of the total market share when it comes to browsers, possibly presenting enough attack surface to make it worthwhile for attackers to explore," Hass says. 

Businesses should also prioritize CVE-2020-0922, a critical RCE flaw in the Microsoft Common Object Model (COM) that would allow an attacker to execute malicious code on a target device by luring a victim to open a specially crafted file or visit a website hosting malicious JavaScript. Today's patch addresses the vulnerability by correcting how COM handles objects in memory.

This fix is important because COM is the base framework of Microsoft services such as ActiveX, OLE, DirectX, and Windows Shell. If the flaw is left unpatched, it could give an attacker a large target to explore when seeking out vulnerabilities in a network, says Richard Melick, senior technical product manager for Automox.

"Given that the exploit can be taken advantage of through a simple malicious JavaScript or website, potentially delivered through a phishing email, it is necessary to address to minimize a network's attack surface," he explains.