CVE-2016-3279 in Office
Summary
by MITRE
Microsoft Office 2010 SP2, Excel 2010 SP2, PowerPoint 2010 SP2, Word 2010 SP2, Excel 2013 SP1, PowerPoint 2013 SP1, Word 2013 SP1, Excel 2013 RT SP1, PowerPoint 2013 RT SP1, Word 2013 RT SP1, Excel 2016, Word 2016, Word Automation Services on SharePoint Server 2010 SP2, and Office Web Apps 2010 SP2 allow remote attackers to execute arbitrary code via a crafted XLA file, aka "Microsoft Office Remote Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 09/01/2022
This vulnerability represents a critical remote code execution flaw in Microsoft Office products that affects multiple versions from 2010 through 2016. The vulnerability specifically manifests when Office applications process specially crafted XLA files, which are Excel add-in files that can contain malicious code. The flaw allows attackers to execute arbitrary commands on affected systems without requiring user interaction, making it particularly dangerous in enterprise environments where Office applications are commonly used. This vulnerability falls under CWE-119, which addresses improper restriction of operations within a recognized security boundary, and aligns with ATT&CK technique T1203, which covers Exploitation for Client Execution through malicious Office documents.
The technical implementation of this vulnerability stems from insufficient input validation in Microsoft Office's handling of XLA file formats. When an Office application opens or processes a maliciously crafted XLA file, the application fails to properly validate the file structure and content, allowing attackers to inject and execute malicious code within the application's memory space. This occurs because the vulnerable applications do not adequately sanitize the XLA file headers, data structures, or embedded code sequences that could be interpreted as executable instructions. The vulnerability is particularly concerning because it can be triggered through various attack vectors including email attachments, web downloads, and malicious Office documents that are automatically processed by Office applications.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise. Successful exploitation allows attackers to gain full control over affected systems, potentially enabling them to install additional malware, establish persistence mechanisms, escalate privileges, or exfiltrate sensitive data. In enterprise environments, this vulnerability could lead to widespread compromise across multiple systems since Office applications are frequently used for document processing and collaboration. The vulnerability affects both desktop Office installations and server-based Office applications including Word Automation Services and Office Web Apps, making it particularly dangerous for organizations that rely on automated document processing or web-based Office services.
Organizations should implement multiple layers of defense to mitigate this vulnerability including immediate deployment of Microsoft security patches and updates, which address the underlying validation issues in Office's XLA file processing. Network-based mitigations such as email filtering and web proxy restrictions can help prevent the delivery of malicious XLA files to end users. Additionally, implementing application whitelisting policies that restrict execution of Office applications from untrusted sources, disabling automatic opening of Office files from the internet, and educating users about the dangers of opening suspicious Office documents are crucial defensive measures. Security monitoring should focus on detecting unusual Office application behavior, unexpected file downloads, and any attempts to execute code from Office-related processes. Organizations should also consider implementing endpoint detection and response solutions that can identify anomalous behavior indicative of exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how seemingly benign file format processing can become a critical security risk when proper validation is lacking.