CVE-2011-0177 in Mac OS X
Summary
by MITRE
Multiple buffer overflows in Apple Type Services (ATS) in Apple Mac OS X before 10.6.7 allow remote attackers to execute arbitrary code via a document that contains a crafted SFNT table in an embedded font.
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Analysis
by VulDB Data Team • 10/21/2021
Apple Type Services represents a critical component within macOS that handles font processing and rendering operations across the operating system. The vulnerability described in CVE-2011-0177 stems from multiple buffer overflow conditions within ATS that occur when processing specially crafted SFNT (Simple Font Number Table) structures embedded within documents. These buffer overflows specifically affect Mac OS X versions prior to 10.6.7, creating a significant security risk that remote attackers can exploit to gain unauthorized code execution privileges. The flaw manifests when the system attempts to parse and render fonts contained within documents, particularly those with malformed SFNT tables that exceed allocated memory boundaries. This vulnerability falls under CWE-121, which categorizes buffer overflow conditions where insufficient space allocation leads to memory corruption. The attack vector involves delivery of malicious documents containing crafted fonts through various means such as email attachments, web downloads, or network shares, making it particularly dangerous in enterprise environments where users frequently interact with untrusted content.
The technical exploitation of this vulnerability leverages the inherent weakness in memory management during font processing operations within Apple Type Services. When ATS encounters an embedded font with an oversized SFNT table, the system's buffer allocation mechanisms fail to properly validate the table size before copying data into fixed-size buffers. This allows attackers to overwrite adjacent memory locations with malicious code, potentially leading to privilege escalation or complete system compromise. The flaw demonstrates characteristics consistent with CWE-125, which describes out-of-bounds read conditions that can be exploited for information disclosure or code execution. The operational impact extends beyond simple code execution to include potential denial of service conditions and data corruption within the affected systems. Attackers can craft documents that appear legitimate but contain hidden malicious font structures, making detection difficult and increasing the likelihood of successful exploitation. The vulnerability affects not only individual user systems but also enterprise environments where document sharing and collaboration are common practices.
The security implications of CVE-2011-0177 align with several tactics described in the MITRE ATT&CK framework, particularly those related to initial access and execution phases. The vulnerability enables adversaries to establish persistent access through document-based attacks that bypass traditional network-based security controls. The exploitation process typically follows the pattern of delivering malicious documents through social engineering or automated delivery mechanisms, followed by code execution on the target system. Organizations using affected macOS versions face significant risk of compromise, especially in environments where users have elevated privileges or access to sensitive data. The vulnerability's remote nature means that attackers do not require physical access to target systems, making it particularly dangerous in cloud environments or remote work scenarios. System administrators should consider implementing document filtering measures and user education programs to reduce the attack surface, though the most effective mitigation involves immediate patch deployment. The flaw represents a classic example of how font processing libraries can become attack vectors, highlighting the importance of robust input validation and memory safety practices in system components that handle untrusted data. Security professionals should monitor for indicators of compromise related to document-based attacks and implement network-based intrusion detection rules targeting the specific exploitation patterns associated with this vulnerability.
Apple addressed this vulnerability through the release of Mac OS X 10.6.7, which included patches to the Apple Type Services component that properly validate SFNT table structures and prevent buffer overflows during font processing. The patch implementation specifically focuses on memory allocation validation and bounds checking mechanisms within ATS, ensuring that font data cannot exceed allocated buffer sizes. Organizations should prioritize immediate deployment of this security update across all affected systems, as the vulnerability remains exploitable in unpatched environments. The resolution demonstrates Apple's commitment to addressing security flaws in core system components, though the incident underscores the ongoing challenge of securing complex font processing systems that must handle diverse and potentially malicious input formats. Security teams should conduct vulnerability assessments to identify any systems still running unsupported macOS versions and implement additional monitoring for suspicious document processing activities that might indicate exploitation attempts.