Pierluigi Paganini May 09, 2017

Microsoft fixes the vulnerability in the Microsoft Malware Protection Engine (CVE-2017-0290) discovered just three days by Google experts.

Last week the researchers at the Google Project Zero team have discovered a new critical Windows RCE vulnerability, tracked as CVE-2017-0290, they defined the bug as the worst Windows RCE in recent memory.

I think @natashenka and I just discovered the worst Windows remote code exec in recent memory. This is crazy bad. Report on the way. 🔥🔥🔥

— Tavis Ormandy (@taviso) May 6, 2017

The researchers only revealed the following information on the Windows RCE vulnerability:

• The PoC exploit the Project Zero team has developed works against default Windows installations.
• The Windows RCE vulnerability could be exploited by a remote attacker.
• The attack is “wormable,” capability to spread itself.

It took Microsoft less than three days to fix the critical RCE flaw that affects the Microsoft Malware Protection Engine.

Still blown away at how quickly @msftsecurity responded to protect users, can't give enough kudos. Amazing.

— Tavis Ormandy (@taviso) May 9, 2017

“Microsoft is releasing this security advisory to inform customers that an update to the Microsoft Malware Protection Engine addresses a security vulnerability that was reported to Microsoft.” reads the advisory published by Microsoft.

“The update addresses a vulnerability that could allow remote code execution if the Microsoft Malware Protection Engine scans a specially crafted file. An attacker who successfully exploited this vulnerability could execute arbitrary code in the security context of the LocalSystem account and take control of the system.

The Microsoft Malware Protection Engine ships with several Microsoft antimalware products.”

The Flaw affects the “MsMpEng” service, which runs unsandboxed with SYSTEM privileges and is accessible without authentication via Windows services such as Exchange and IIS.

The list of affected software includes Forefront Endpoint Protection, Endpoint Protection, Forefront Security for SharePoint Service Pack 3, System Center Endpoint Protection, Security Essentials, Windows Defender, and Windows Intune Endpoint Protection.

“MsMpEng is the Malware Protection service that is enabled by default on Windows 8, 8.1, 10, Windows Server 2012, and so on. Additionally, Microsoft Security Essentials, System Centre Endpoint Protection and various other Microsoft security products share the same core engine. MsMpEng runs as NT AUTHORITY\SYSTEM without sandboxing, and is remotely accessible without authentication via various Windows services, including Exchange, IIS, and so on.” reads the advisory published by the Google Project Zero Team.”

The Google Project Zero researchers said the vulnerability can be exploited via email – opening the malicious email is not necessary for exploitation – or by getting the targeted user to access a specially crafted link.

“Vulnerabilities in MsMpEng are among the most severe possible in Windows, due to the privilege, accessibility, and ubiquity of the service.” added Google.

“This level of accessibility is possible because MsMpEng uses a file system minifilter to intercept and inspect all system filesystem activity, so writing controlled contents to anywhere on disk (e.g. caches, temporary internet files, downloads (even unconfirmed downloads), attachments, etc) is enough to access functionality in mpengine,” the experts said in their advisory.

The experts highlighted that on workstations, attackers can access mpengine just by sending emails to users (reading the email or opening attachments is not necessary), visiting links in a web browser, instant messaging and so on.

According to Microsoft, the security fix should be sent out automatically to antimalware products that use the Microsoft Malware Protection Engine within 48 hours.

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Pierluigi Paganini

(Security Affairs –  Windows RCE vulnerability, Microsoft Malware Protection Engine)

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