Microsoft Patch Tuesday Fixes Windows Bugs Under Attack

Microsoft today issued its April batch of security fixes, which patches 74 vulnerabilities including two Windows zero-days under active attack.

CVE-2019-0803 and CVE-2019-0859 both patch Windows elevation of privilege bugs found exploited in the wild. Microsoft describes both patches in a similar manner: In short, a vulnerability exists when the Win32k component doesn't properly handle objects in memory. An attacker could exploit this to run malicious code in kernel mode and install programs; view, change, or delete data; or create a new account with full user rights.

If this sounds familiar, it's likely because last month's Patch Tuesday also addressed two zero-day elevation-of-privilege vulnerabilities in Windows. Both were rated Important in severity, enabling an attacker with system access to increase their privileges and take over the system.

"This has been a trend in several Patch Tuesday releases, where researchers have reported Win32k elevation of privilege bugs leveraged by attackers as zero-days, which begs the question of just how many of these vulnerabilities attackers have stockpiled," notes Satnam Narang, senior research engineer at Tenable, in response to today's security updates.

As in March, one of these flaws (CVE-2019-0859) was reported by Kaspersky Lab. CVE-2019-0803 was found by the Alibaba Cloud Intelligence Security Team. Both are classified as Important in severity. There is no indication of how the bugs are being used in the wild; however, the discovery by Kaspersky Labs is a sign either or both could have been used in targeted malware.

Windows zero-days aside, a few other patches warrant attention to this month. One of these is CVE-2019-0853, a GDI+ remote code execution (RCE) bug categorized as Critical. A bug exists in how the Windows Graphic Design Interface handles objects in memory. Attackers who successfully exploit the bug could take over an affected system, and they could do so by tricking people into visiting a malicious website or downloading a bad attachment.

Several Microsoft products, including Windows and the Office suite, use the GDI+ component. Given how this bug can be exploited remotely, security admins are advised to prioritize this one when rolling out updates.

Among the other remote code execution vulnerabilities patched this month is CVE-2019-0822, an RCE flaw that exists in the way the Microsoft Graphics Components handle objects in memory. To exploit it, an attacker could send the victim a specially crafted file. There are also a handful of RCE bugs (CVE-2019-0824, CVE-2019-0825, CVE-2019-0826, CVE-2019-0827) that exist when Microsoft Office Access Connectivity Engine improperly handles objects in memory.

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