Security Experts:

Critical Vulnerability Patched in Microsoft Malware Protection Engine

An update released this week by Microsoft for its Malware Protection Engine patches a vulnerability that can be exploited to take control of a system by placing a malicious file in a location where it would be scanned.

The Microsoft Malware Protection Engine provides scanning, detection and cleaning capabilities for security software made by the company. The engine is affected by a flaw that can be exploited for remote code execution when a specially crafted file is scanned.

The malicious file can be delivered via a website, email or instant messenger. The Malware Protection Engine will automatically scan the file (if real-time protection is enabled) and allow the attacker to execute arbitrary code in the context of the LocalSystem account, which can lead to a complete takeover of the targeted system.

On systems where real-time scanning is not enabled, the exploit will still get triggered, but only when a scheduled scan is initiated.

The vulnerability, tracked as CVE-2018-0986 and rated “critical,” affects several Microsoft products that use the Malware Protection Engine, including Exchange Server, Forefront Endpoint Protection 2010, Security Essentials, Windows Defender, and Windows Intune Endpoint Protection.

While the flaw is dangerous and easy to exploit, Microsoft believes exploitation is “less likely.” The company pointed out that the patch for this vulnerability will be automatically delivered to customers within 48 hours of release – users and administrators do not have to take any action.

Google Project Zero researcher Thomas Dullien, aka “Halvar Flake,” has been credited for finding CVE-2018-0986. The details of the vulnerability have yet to be disclosed, but considering that the patch is being delivered automatically to most systems, the information will likely become available soon.

This is not the first time Google Project Zero researchers have discovered critical vulnerabilities in Microsoft’s Malware Protection Engine. While Google may occasionally disclose flaws in Microsoft products before patches become available, in the case of the Malware Protection Engine, Microsoft typically releases patches within a few days or weeks.

A similar flaw in the Malware Protection Engine was also found recently by employees of UK's National Cyber Security Centre (NCSC).

UPDATE: The details of the vulnerability have been made public by Google Project Zero.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.