CVE-2016-7266 in Office
Summary
by MITRE
Microsoft Excel 2007 SP3, Excel 2010 SP2, Excel 2013 SP1, Excel 2013 RT SP1, Excel 2016, Office Compatibility Pack SP3, Excel Viewer, and Excel 2016 for Mac mishandle a registry check, which allows user-assisted remote attackers to execute arbitrary commands via crafted embedded content in a document, aka "Microsoft Office Security Feature Bypass Vulnerability."
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Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2016-7266 represents a critical security flaw in Microsoft Excel software versions spanning multiple platforms and editions. This issue stems from an improper registry check implementation that creates a pathway for malicious actors to bypass security measures designed to protect users from harmful content. The vulnerability affects a broad range of Microsoft Office products including Excel 2007 through 2016 across different operating systems and compatibility packs, making it particularly concerning for enterprise environments where these applications are widely deployed. The flaw specifically targets the security validation mechanisms that should prevent execution of potentially dangerous embedded content within Excel documents.
The technical implementation of this vulnerability involves a registry check that fails to properly validate the security context of embedded content within Excel files. When users open maliciously crafted documents, the flawed registry validation allows attackers to manipulate the security environment in a way that permits arbitrary code execution. This occurs because the system does not adequately verify the integrity and source of embedded objects, particularly those that might contain malicious macros or other executable components. The vulnerability exploits the trust relationship between the application and its registry-based security policies, enabling attackers to circumvent the intended security boundaries that should isolate potentially harmful content.
From an operational perspective, this vulnerability presents significant risks to organizations as it requires only user interaction to exploit successfully. Attackers can craft malicious Excel documents containing embedded content that triggers the registry bypass mechanism when opened by victims. The remote execution capability means that attackers can deliver payloads through various vectors including email attachments, web downloads, or compromised file sharing systems. Once exploited, the vulnerability allows attackers to execute arbitrary commands with the privileges of the affected user, potentially leading to complete system compromise, data exfiltration, or further network infiltration. The user-assisted nature of the attack means that social engineering elements may be required to convince targets to open malicious documents, but the actual exploitation mechanism remains relatively straightforward for skilled attackers.
Organizations should implement immediate mitigations including applying the relevant Microsoft security patches released in response to this vulnerability. The mitigation strategy should also incorporate enhanced document scanning procedures and user education about the risks of opening untrusted Excel files. Network-based protections such as email filtering and web proxies can help reduce the likelihood of users encountering malicious documents. Additionally, implementing application whitelisting policies and restricting user privileges can limit the potential impact if exploitation occurs. Security teams should also monitor for indicators of compromise related to this vulnerability, particularly unusual registry modifications or unexpected command executions. The vulnerability aligns with CWE-284 Access Control Issues and maps to ATT&CK techniques involving privilege escalation and execution through office applications, making it particularly relevant for organizations following established cybersecurity frameworks and threat modeling approaches.