CVE-2011-0033 in Windows
Summary
by MITRE
The OpenType Compact Font Format (CFF) 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 validate parameter values in OpenType fonts, which allows remote attackers to execute arbitrary code via a crafted font, aka "OpenType Font Encoded Character Vulnerability."
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Analysis
by VulDB Data Team • 01/26/2025
The vulnerability identified as CVE-2011-0033 represents a critical security flaw within the OpenType Compact Font Format driver implementation across multiple Microsoft Windows operating systems. This weakness resides in how the system processes font parameter validation, specifically within the CFF driver component that handles font rendering operations. The flaw affects Windows XP Service Pack 2 and 3, Windows Server 2003 Service Pack 2, Windows Vista Service Pack 1 and 2, Windows Server 2008 Gold and Service Pack 2, Windows Server 2008 R2, and Windows 7 operating systems. The vulnerability operates at the kernel level font processing subsystem, making it particularly dangerous as it can be exploited through font rendering operations that occur during normal system operations.
The technical exploitation of this vulnerability stems from improper parameter validation within the CFF driver's font parsing routines. When the system processes OpenType fonts containing specially crafted parameter values, the driver fails to properly validate input data before processing it, leading to potential memory corruption conditions. This validation failure creates opportunities for attackers to manipulate font parameters in ways that can trigger buffer overflows or other memory corruption scenarios. The flaw specifically manifests when the CFF driver encounters malformed or maliciously constructed font data that it cannot properly handle during the font decoding process. This vulnerability falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions that can lead to arbitrary code execution, and aligns with ATT&CK technique T1059.007 for process injection and T1203 for exploitation for execution.
The operational impact of this vulnerability extends beyond simple remote code execution capabilities, as it provides attackers with a mechanism to compromise entire systems through font-based attacks. Attackers can deliver malicious fonts through various vectors including email attachments, web downloads, or network shares, making the attack surface particularly broad. The vulnerability can be exploited without user interaction in many scenarios, as font rendering occurs automatically when systems display documents or web pages containing embedded fonts. This makes the vulnerability particularly dangerous in enterprise environments where users frequently encounter fonts from various sources. The exploitation can result in complete system compromise, allowing attackers to install malware, steal data, or establish persistent access to affected systems. The vulnerability's presence in multiple Windows versions also means that organizations across different platform versions need to implement coordinated patching strategies to address the issue effectively.
Mitigation strategies for CVE-2011-0033 focus on immediate patch deployment and operational security measures to reduce exposure. Microsoft released security updates that address the font validation issues in the CFF driver component, requiring administrators to apply these patches across all affected systems. Organizations should implement network-level controls to block font file types from suspicious sources and consider disabling font rendering for untrusted content. The implementation of application whitelisting solutions can prevent execution of unauthorized font files, while regular security assessments should monitor for potential exploitation attempts. Additionally, system administrators should consider disabling unnecessary font rendering capabilities where possible and implement monitoring for unusual font processing activities. Security teams should also establish incident response procedures specifically addressing font-based vulnerabilities and maintain updated threat intelligence feeds to track exploitation attempts targeting this vulnerability.