CVE-2016-7267 in Office
Summary
by MITRE
Microsoft Excel 2010 SP2, 2013 SP1, 2013 RT SP1, and 2016 misparses file formats, which makes it easier for remote attackers to execute arbitrary code via a crafted document, aka "Microsoft Office Security Feature Bypass Vulnerability."
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/08/2022
The vulnerability identified as CVE-2016-7267 represents a critical security flaw in Microsoft Excel versions 2010 SP2, 2013 SP1, 2013 RT SP1, and 2016 that stems from improper file format parsing mechanisms. This vulnerability allows remote attackers to bypass security features designed to protect against malicious code execution, creating a significant attack surface for malicious document delivery. The flaw specifically manifests in how Excel processes certain file format elements, leading to potential code execution when users open compromised documents. According to CWE-129, this vulnerability falls under improper input validation, where the application fails to properly validate or sanitize input data during file parsing operations, creating an environment where malicious code can be executed without proper authorization. The security feature bypass aspect of this vulnerability directly relates to Microsoft's Office security model, which relies on various protection mechanisms to prevent unauthorized code execution within office applications. This particular weakness enables attackers to circumvent the security controls that normally would prevent malicious code from running when users open documents.
The technical implementation of this vulnerability involves the manipulation of Excel file format structures that cause the application to misinterpret certain data elements during parsing. When Excel encounters a crafted document containing maliciously constructed file format elements, the parser fails to properly validate the structure and executes code as if it were legitimate content. This misparsing occurs in the file format handling layer of Excel, where the application's parser does not adequately verify the integrity of the file structure before attempting to execute code contained within it. The vulnerability operates through a combination of buffer manipulation and code execution chaining, where attackers can construct documents that appear legitimate to users while containing hidden malicious code. This behavior aligns with ATT&CK technique T1204.002, which describes the use of malicious files to execute code through legitimate applications, and T1059.005, which covers the execution of code through scripting languages or application-specific environments. The specific nature of this vulnerability makes it particularly dangerous because it can be delivered through email attachments, web downloads, or other common attack vectors that users typically trust.
The operational impact of CVE-2016-7267 extends beyond simple code execution to potentially enable full system compromise when users open malicious documents. Attackers can leverage this vulnerability to deploy malware, establish persistence mechanisms, or gain unauthorized access to sensitive information within the target environment. The vulnerability's remote exploitation capability means that attackers can deliver malicious documents through various channels without requiring physical access to the target system. Organizations running affected Excel versions face significant risk of targeted attacks, especially in environments where users frequently open email attachments or download documents from untrusted sources. The security implications are compounded by the fact that this vulnerability affects multiple versions of Microsoft Office, creating widespread exposure across different organizational environments. According to industry best practices for vulnerability management, this flaw represents a high-priority issue that requires immediate remediation through security updates or temporary mitigations. The vulnerability's potential for privilege escalation and lateral movement within networks makes it particularly concerning for enterprise environments where Excel is commonly used for business operations and document sharing.
Mitigation strategies for CVE-2016-7267 should include immediate application of Microsoft security updates that address the file format parsing vulnerability in affected Excel versions. Organizations should implement strict document handling policies that require verification of all incoming documents before opening them, particularly those received via email or downloaded from external sources. Network-based protections such as email filtering and web application firewalls can help reduce the likelihood of users encountering malicious documents. Microsoft recommends enabling the Office Protected View feature, which provides an additional layer of security by opening documents in a restricted environment that prevents automatic code execution. Security awareness training for end users remains crucial in preventing successful exploitation, as many attacks rely on social engineering techniques to convince users to open malicious documents. Additionally, implementing application whitelisting policies that restrict the execution of unauthorized applications can help prevent exploitation even if a user inadvertently opens a malicious document. The vulnerability's classification as a security feature bypass makes it particularly important to maintain updated security configurations and ensure that all Office applications are running with the latest security patches. Organizations should also consider implementing monitoring solutions that can detect unusual document opening patterns or attempts to execute code through Office applications, providing early warning capabilities for potential exploitation attempts.