CVE-2017-8542 in Windows
Summary
by MITRE
The Microsoft Malware Protection Engine running on Microsoft Forefront and Microsoft Defender on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016, Microsoft Exchange Server 2013 and 2016, does not properly scan a specially crafted file leading to denial of service. aka "Microsoft Malware Protection Engine Denial of Service Vulnerability", a different vulnerability than CVE-2017-8535, CVE-2017-8536, CVE-2017-8537, and CVE-2017-8539.
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Analysis
by VulDB Data Team • 06/05/2020
The Microsoft Malware Protection Engine vulnerability CVE-2017-8542 represents a critical denial of service flaw that specifically affects Microsoft's antivirus scanning capabilities across multiple operating systems and server platforms. This vulnerability resides within the core malware protection engine component that powers both Microsoft Forefront and Microsoft Defender solutions, making it particularly dangerous as it impacts the fundamental security functionality of these widely deployed protection systems. The flaw manifests when the engine processes specially crafted malicious files that trigger an abnormal termination of the scanning process, effectively rendering the antivirus protection unavailable for legitimate threat detection.
The technical implementation of this vulnerability stems from inadequate input validation within the malware scanning engine's file parsing routines. When encountering specifically crafted files that exploit memory handling inconsistencies or buffer overflow conditions, the engine fails to properly handle the malformed input and subsequently crashes or becomes unresponsive. This behavior aligns with common software security weaknesses categorized under CWE-129 and CWE-125, which address improper input validation and buffer overflow conditions respectively. The vulnerability demonstrates how even defensive security software can contain exploitable flaws that undermine their protective capabilities.
The operational impact of CVE-2017-8542 extends beyond simple service disruption as it fundamentally compromises the security posture of affected systems. Organizations relying on Microsoft Defender or Forefront for endpoint protection face a scenario where their primary defense mechanism becomes unavailable, leaving systems vulnerable to actual malware infections while the protection system itself is non-functional. This creates a particularly dangerous situation where security teams may be unaware of the vulnerability's presence, as the denial of service occurs silently during routine scanning operations. The attack surface includes all supported Microsoft Windows platforms and Exchange Server versions, making it a widespread concern across enterprise environments.
Mitigation strategies for this vulnerability require immediate patch application from Microsoft, as the company released security updates specifically addressing the engine's handling of malformed files. Organizations should prioritize deployment of these patches across all affected systems, particularly those running Windows Server 2008 and 2012 versions, as well as Windows 7, 8.1, and 10 clients. Additionally, implementing network segmentation and monitoring for unusual scanning behavior can help detect exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 (Unauthorized Remote Commands) and T1070.004 (File Deletion) as attackers could potentially use this to disable security protections or create conditions for more sophisticated attacks. System administrators should also consider temporarily disabling real-time scanning during patch deployment to prevent triggering the vulnerability during update processes, while maintaining other security measures to protect against active threats.