CVE-2015-6106 in Office
Summary
by MITRE
The Windows font library in Microsoft Windows Vista SP2, Windows Server 2008 SP2, Office 2007 SP3, Office 2010 SP2, Word Viewer, Skype for Business 2016, Lync 2010, Lync 2013 SP1, and Live Meeting 2007 Console allows remote attackers to execute arbitrary code via a crafted embedded font, aka "Graphics Memory Corruption Vulnerability."
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Analysis
by VulDB Data Team • 06/30/2022
The vulnerability identified as CVE-2015-6106 represents a critical graphics memory corruption flaw within the Windows font library that affects multiple Microsoft products including Windows Vista SP2 and Windows Server 2008 SP2. This vulnerability stems from improper handling of embedded fonts during rendering operations, creating a pathway for remote code execution attacks. The flaw specifically manifests when the system processes crafted embedded font files that contain maliciously constructed font data, leading to memory corruption that can be exploited by attackers to execute arbitrary code with the privileges of the affected application.
This vulnerability operates at the intersection of graphics rendering and memory management within Microsoft's font processing subsystem, making it particularly dangerous as it can be triggered through various attack vectors including email attachments, web downloads, and document files. The technical implementation involves the font library's failure to properly validate font structure parameters when parsing embedded fonts, allowing attackers to craft font files that cause buffer overflows or memory corruption during rendering operations. The vulnerability is classified under CWE-125 as an out-of-bounds read condition, though the actual exploitation mechanism involves memory corruption that enables code execution. According to ATT&CK framework, this represents a technique categorized under T1203 - Exploitation for Client Execution, where adversaries leverage software vulnerabilities to execute malicious code on target systems.
The operational impact of CVE-2015-6106 is substantial across the affected Microsoft product ecosystem, as it provides attackers with a reliable method for remote code execution without requiring user interaction in many scenarios. The vulnerability affects both desktop and server operating systems, making it particularly attractive to threat actors targeting enterprise environments where these products are commonly deployed. Attackers can leverage this vulnerability through various attack vectors including phishing emails containing malicious documents, compromised websites serving malicious font files, or through social engineering tactics that trick users into opening infected files. The exploitation process typically involves crafting a specially formatted font file that, when processed by the vulnerable Windows font library, causes memory corruption leading to arbitrary code execution.
Mitigation strategies for CVE-2015-6106 should focus on immediate patch deployment as the primary defense mechanism, with Microsoft releasing security updates that address the font parsing vulnerabilities. Organizations should implement network segmentation and access controls to limit exposure, particularly for systems that process untrusted documents or files. Additional defensive measures include disabling automatic font embedding in applications, implementing strict file validation policies, and monitoring for suspicious font-related network traffic. Security teams should also consider deploying application whitelisting solutions that restrict execution of untrusted font processing components, while maintaining regular vulnerability assessments to identify and remediate similar weaknesses in other software components. The vulnerability demonstrates the importance of proper input validation and memory management in graphics rendering libraries, highlighting the need for comprehensive security testing of font processing functionality in enterprise software environments.