Microsoft late yesterday issued an emergency patch for its major Windows malware protection tool that fixes a critical vulnerability discovered by the UK's National Cyber Security Centre (NCSC), an arm of the Government Communications Headquarters (GCHQ) intelligence agency.
The remote code execution vulnerability (CVE-2017-11937) in the Microsoft Malware Protection Engine would allow an attacker to gain full control of Windows 7, 8, 10, and Windows Server systems via the Windows Defender feature that uses it. Also affected by the flaw are Microsoft Endpoint Protection, Microsoft Exchange Server 2013 and 2016, Microsoft Forefront Endpoint Protection, Microsoft Forefront Endpoint Protection 2010, and Microsoft Security Essentials.
"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. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights," Microsoft said in its security alert.
An exploit would require a "special crafted file" be scanned by the malware protection engine, and the malicious file could be served to a victim via email, a website, instant message, or via a hosting server, Microsoft said. Systems with Windows real-time protection enabled automatically get updated with the patch.
See Microsoft's advisory here for more details.