CVE-2010-3956 in Windows
Summary
by MITRE
The OpenType Font (OTF) driver in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, and R2, and Windows 7 does not properly perform array indexing, which allows local users to gain privileges via a crafted OpenType font, aka "OpenType Font Index Vulnerability."
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Analysis
by VulDB Data Team • 03/18/2021
The OpenType Font Index Vulnerability represents a critical privilege escalation flaw within Microsoft's font rendering subsystem that affects multiple versions of the windows operating system. This vulnerability resides in the OpenType Font driver component responsible for processing font files within the windows environment. The flaw manifests when the system processes specially crafted OpenType font files that contain malformed array indexing operations during font rendering processes. The vulnerability specifically targets the way the font driver handles memory allocation and array bounds checking when parsing font data structures, creating a condition where array indices can exceed valid memory boundaries.
The technical exploitation of this vulnerability occurs through local code execution within the context of the affected windows systems. When a malicious user presents a specially crafted OpenType font file to a vulnerable system, the font driver fails to properly validate array bounds during font processing operations. This improper array indexing allows an attacker to manipulate memory locations that should remain protected, potentially leading to arbitrary code execution with elevated privileges. The vulnerability operates at the kernel level where font rendering occurs, making it particularly dangerous as it can be leveraged to bypass standard user privilege restrictions and gain system-level access. This type of flaw aligns with CWE-129 which describes improper validation of array index values, and CWE-787 which addresses out-of-bounds write operations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a reliable method to gain system administrator access on vulnerable systems. Local users who can convince a victim to view a malicious font file or execute a font-based attack can potentially compromise entire systems without requiring network access or complex exploitation techniques. The vulnerability affects a broad range of windows operating systems including legacy versions like windows xp and server 2003, as well as newer releases such as windows vista and windows 7. Attackers can leverage this vulnerability to establish persistent access, escalate privileges, and potentially move laterally within network environments. The attack vector is particularly concerning because font files are commonly encountered in various legitimate contexts such as email attachments, web pages, and document processing.
Mitigation strategies for this vulnerability require immediate patch application from microsoft, as the primary defense against this specific flaw. System administrators should ensure all affected windows systems receive the relevant security updates from microsoft's security bulletin. Additional protective measures include implementing strict file execution policies that prevent execution of font files from untrusted sources, disabling automatic font rendering where possible, and monitoring for unusual font processing activity. Network segmentation and privilege separation can help limit the potential impact if exploitation occurs. The vulnerability demonstrates the importance of proper bounds checking in system-level components and highlights the need for comprehensive security testing of font rendering engines. Organizations should also consider implementing application whitelisting policies to prevent execution of untrusted font files. This vulnerability serves as a reminder of the critical security implications of font processing components and the potential for privilege escalation through seemingly benign file formats, aligning with attack patterns documented in the mitre attack framework under privilege escalation techniques.