CVE-2011-0176 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 embedded Type 1 font.
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Analysis
by VulDB Data Team • 10/21/2021
Apple Type Services represents a critical component within macOS responsible for handling font rendering and processing across the operating system. The vulnerability described in CVE-2011-0176 exploits multiple buffer overflow conditions within this framework, specifically targeting the processing of Type 1 fonts embedded within documents. These buffer overflows occur when the ATS subsystem attempts to parse malformed or specially crafted Type 1 font data, creating opportunities for attackers to manipulate memory layout and execute arbitrary code with the privileges of the affected application. The vulnerability affects Mac OS X versions prior to 10.6.7, indicating that the flaw existed for several years before Apple issued a patch. The attack vector involves remote code execution through document files containing maliciously constructed font data, making it particularly dangerous in email attachments, web downloads, or file sharing scenarios. This vulnerability directly maps to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1059.007 for command and script interpreter execution. The operational impact extends beyond simple code execution, as successful exploitation could allow attackers to escalate privileges, install malware, or establish persistent access to affected systems. The nature of the vulnerability suggests it could be leveraged in targeted attacks against specific users or organizations, particularly those using older macOS versions where patching may be delayed. The complexity of font processing within ATS makes this class of vulnerability particularly challenging to defend against, as legitimate font processing is essential for proper system functionality. Attackers could craft documents that appear benign to users while containing hidden malicious font data designed to trigger the buffer overflow conditions during normal document viewing or printing operations. This vulnerability demonstrates the inherent risks of rich document processing and the critical importance of proper input validation in font handling systems. The exploitability of this vulnerability highlights the need for comprehensive security updates and the dangers of running outdated operating systems in enterprise environments. Organizations should prioritize immediate patching of affected systems and implement network monitoring to detect potential exploitation attempts. The vulnerability also underscores the importance of sandboxing mechanisms and privilege separation in preventing the escalation of privilege during exploitation attempts.
The technical implementation of this vulnerability involves the manipulation of font data structures during parsing operations within Apple Type Services. When ATS encounters a Type 1 font embedded in a document, it performs various operations including memory allocation, data copying, and format validation that can be exploited through carefully crafted input data. The buffer overflow conditions typically manifest when the system attempts to copy font data into fixed-size buffers without proper bounds checking, allowing attackers to overwrite adjacent memory locations. This memory corruption can be manipulated to redirect program execution flow, potentially executing attacker-controlled code. The vulnerability's remote nature means that exploitation can occur without user interaction beyond opening a malicious document, making it particularly dangerous in phishing scenarios or automated attack campaigns. Security researchers have noted that similar vulnerabilities in font processing systems have been exploited in the wild, particularly targeting enterprise users who may be running older macOS versions. The patch provided by Apple addresses the underlying buffer overflow conditions by implementing proper bounds checking and input validation for font data processing. Organizations should consider implementing additional security controls such as email filtering, web application firewalls, and endpoint detection systems to provide defense-in-depth against potential exploitation attempts. The vulnerability also demonstrates the importance of regular security assessments and vulnerability management processes, as the exploitation of such flaws can have significant business impact and regulatory implications.