CVE-2016-7236 in Excel
Summary
by MITRE
Microsoft Excel 2010 SP2, Excel for Mac 2011, Excel 2016 for Mac, and Excel Services on SharePoint Server 2010 SP2 allow remote attackers to execute arbitrary code via a crafted Office document, aka "Microsoft Office Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 09/30/2022
This vulnerability represents a critical memory corruption flaw in Microsoft Excel software across multiple platforms and versions including Excel 2010 SP2, Excel for Mac 2011, Excel 2016 for Mac, and Excel Services on SharePoint Server 2010 SP2. The vulnerability stems from improper handling of specially crafted Office documents that trigger memory corruption during document processing, creating opportunities for remote code execution. The flaw manifests when Excel attempts to parse maliciously constructed file structures, leading to unpredictable memory behavior that attackers can exploit to gain unauthorized system access. This vulnerability falls under the CWE-125 weakness category, which encompasses out-of-bounds read conditions that can result in memory corruption and arbitrary code execution. From an operational perspective, the vulnerability presents significant risk to organizations relying on Microsoft Office suites for document processing, as attackers can leverage this flaw to execute malicious code on target systems without requiring local access. The attack vector is particularly dangerous because it operates over remote network connections, allowing threat actors to deliver malicious Office documents through email attachments, web downloads, or compromised websites. The vulnerability aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities for privilege escalation and system compromise. The memory corruption aspect of this vulnerability creates a pathway for attackers to manipulate program execution flow, potentially enabling them to execute shellcode or other malicious payloads directly within the Excel process memory space. Organizations utilizing these affected Excel versions face elevated risk of data breaches, system compromise, and potential lateral movement within their network infrastructure.
The technical exploitation of this vulnerability requires attackers to craft specific Office document formats that trigger the memory corruption behavior in Excel's parsing engine. When a user opens the malicious document, Excel's internal memory management routines fail to properly validate input data structures, leading to buffer overflows or other memory corruption scenarios. The vulnerability is particularly concerning because it operates at the application level, bypassing many traditional network security controls that focus on network-level threats. Attackers typically leverage this vulnerability through social engineering campaigns that deliver malicious documents to unsuspecting users, who then execute the malicious code upon opening the file. The memory corruption occurs during the document parsing phase, where Excel attempts to process complex formatting or embedded objects within the Office file structure. This flaw demonstrates the inherent complexity of modern office document formats and the challenges in properly validating the vast array of possible file structures and content types. The vulnerability's impact extends beyond individual system compromise to potentially affect entire organizational networks, as successful exploitation can provide attackers with persistent access to target systems. Microsoft's security advisory for this vulnerability highlights the need for immediate patch deployment across all affected systems, as the window for exploitation remains open until proper security updates are applied.
Mitigation strategies for this vulnerability involve immediate implementation of Microsoft security patches and updates, as well as network-based protections such as email filtering and web content filtering to prevent delivery of malicious Office documents. Organizations should implement strict document validation policies, including disabling macros in Office documents and restricting file type associations for potentially dangerous formats. Network administrators should consider deploying intrusion detection systems that can identify suspicious Office document traffic patterns and monitor for exploitation attempts. The vulnerability's nature makes it particularly susceptible to defense-in-depth approaches, where multiple layers of security controls work together to prevent successful exploitation. Security teams should also conduct regular vulnerability assessments to identify systems running affected Excel versions and prioritize patching efforts accordingly. Implementation of endpoint protection solutions with behavioral monitoring capabilities can help detect anomalous execution patterns that may indicate exploitation attempts. From a compliance standpoint, organizations should ensure their security measures align with industry standards such as those outlined in the NIST Cybersecurity Framework and ISO 27001 requirements for vulnerability management. The vulnerability's classification as a remote code execution flaw necessitates continuous monitoring of threat intelligence feeds for related exploitation attempts and zero-day variants. Regular security awareness training for end users remains crucial in preventing successful social engineering attacks that leverage this vulnerability, as human factors often represent the primary attack surface for such exploits.