CVE-2017-11935 in Excel
Summary
by MITRE
Microsoft Office 2016 Click-to-Run (C2R) allows a remote code execution vulnerability due to the way files are handled in memory, aka "Microsoft Excel Remote Code Execution Vulnerability".
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Analysis
by VulDB Data Team • 01/27/2021
The vulnerability identified as CVE-2017-11935 represents a critical remote code execution flaw in Microsoft Office 2016 Click-to-Run edition that stems from improper memory handling during file processing operations. This vulnerability specifically affects the Excel application component within the Office suite and enables attackers to execute arbitrary code on vulnerable systems. The flaw exists in the way the application manages memory structures when parsing certain file formats, creating opportunities for malicious actors to exploit the memory corruption issues through specially crafted malicious files. The vulnerability is particularly concerning because it can be triggered through various attack vectors including email attachments, web downloads, or malicious documents that users might encounter during normal office operations. According to the Common Weakness Enumeration catalog, this vulnerability maps to CWE-125, which describes out-of-bounds read conditions that can lead to memory corruption and arbitrary code execution. The attack surface is broad as it affects the widely deployed Office 2016 Click-to-Run version, which represents a significant portion of enterprise and consumer deployments.
The technical exploitation of this vulnerability occurs when a user opens a maliciously crafted Excel file that contains specially constructed data structures designed to trigger memory corruption during the parsing process. The flaw manifests when the application attempts to process certain data elements within the file, leading to improper memory management that allows attackers to overwrite critical memory locations or execute malicious code within the context of the Office application. The vulnerability's exploitation typically requires user interaction through opening a malicious document, making it a prime candidate for phishing attacks or social engineering campaigns. Attackers can leverage this vulnerability to gain full control of affected systems, potentially leading to data theft, system compromise, or further lateral movement within networks. The Office application's memory handling mechanisms fail to properly validate input data before processing, creating a pathway for attackers to inject and execute malicious code. This type of vulnerability aligns with ATT&CK technique T1059 which covers command and scripting interpreter usage, as successful exploitation often involves executing malicious code through the compromised Office application.
The operational impact of CVE-2017-11935 extends beyond individual system compromise to encompass potential enterprise-wide security breaches, particularly in environments where users frequently interact with external documents or email attachments. Organizations utilizing Office 2016 Click-to-Run editions face significant risk exposure, as the vulnerability can be exploited through multiple attack vectors including email-based campaigns, malicious websites, or compromised documents shared through collaboration platforms. The remote code execution capability means that attackers can perform actions such as installing additional malware, modifying system configurations, accessing sensitive data, or establishing persistence mechanisms within the compromised environment. Security teams must consider the implications of this vulnerability when assessing their overall security posture, as it can serve as a gateway for more sophisticated attacks. The vulnerability's exploitation often occurs without user awareness, making detection challenging and increasing the potential for extended compromise periods. Organizations should implement comprehensive monitoring solutions to detect anomalous behavior patterns that may indicate exploitation attempts, particularly around Office application memory usage and file access patterns.
Mitigation strategies for CVE-2017-11935 should include immediate deployment of Microsoft security updates and patches that address the memory handling issues within the Office application. System administrators should implement application whitelisting policies to restrict execution of unauthorized binaries and reduce the attack surface available to potential exploiters. Network security controls such as email filtering, web proxies, and content inspection systems should be configured to block potentially malicious Office documents from entering the organization's network perimeter. Regular security awareness training programs should emphasize the importance of not opening suspicious email attachments or documents from untrusted sources, as user interaction remains a critical component of exploitation. Additionally, organizations should consider implementing endpoint detection and response solutions that can monitor for suspicious memory access patterns or file execution behaviors that may indicate exploitation attempts. The vulnerability's classification as a remote code execution flaw necessitates a layered security approach that combines traditional perimeter defenses with behavioral monitoring and incident response capabilities to effectively defend against potential exploitation attempts.