CVE-2015-3680 in Mac OS X
Summary
by MITRE
Apple Type Services (ATS) in Apple OS X before 10.10.4 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted font file, a different vulnerability than CVE-2015-3679, CVE-2015-3681, and CVE-2015-3682.
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Analysis
by VulDB Data Team • 05/22/2022
Apple Type Services represents a critical component within Apple's operating systems responsible for font handling and rendering across various applications and system interfaces. This subsystem processes font files to display text and graphics, making it a prime target for attackers seeking to exploit memory corruption vulnerabilities. The vulnerability in question affects Apple OS X versions prior to 10.10.4, where the ATS implementation contains a flaw that can be triggered through malformed font data. When a malicious font file is processed by the system, it causes memory corruption that can lead to arbitrary code execution or system crashes, representing a significant security risk to users of affected versions.
The technical nature of this vulnerability stems from insufficient input validation within the font processing pipeline of Apple Type Services. Attackers can craft specially designed font files that contain malformed data structures or oversized elements that exceed buffer boundaries when processed by the ATS subsystem. This memory corruption occurs during the parsing and rendering phases of font handling, where the system fails to properly validate the size and structure of font components before allocating memory for their processing. The flaw allows attackers to manipulate memory layout and potentially execute malicious code with the privileges of the user running the application that processes the font file. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of how untrusted input can lead to arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include full system compromise capabilities. Remote attackers can deliver malicious font files through various attack vectors such as email attachments, web downloads, or compromised websites, making the attack surface particularly broad. When a user opens an application that displays text using the affected font, the malicious font triggers the vulnerability, potentially allowing attackers to gain persistent access to the compromised system. This vulnerability particularly affects applications that automatically render fonts without user interaction, such as web browsers, email clients, and document viewers. The attack chain typically involves the user opening a malicious font file or visiting a compromised website that loads the malicious font, triggering the memory corruption and enabling remote code execution.
Mitigation strategies for this vulnerability require immediate system updates to Apple OS X 10.10.4 or later versions where the fix has been implemented. Organizations should prioritize patch management to ensure all affected systems receive the security updates. Additional protective measures include implementing application sandboxing, restricting font file processing in web browsers, and deploying network-based intrusion detection systems to monitor for suspicious font-related activity. Security teams should also consider restricting user access to potentially malicious font files through email filtering and web content restrictions. This vulnerability demonstrates the importance of proper input validation and memory safety practices in system components that process untrusted data, aligning with ATT&CK technique T1059.007 for scripting and T1203 for exploitation of remote services. The incident highlights the critical need for regular security assessments and timely patch deployment to protect against zero-day vulnerabilities in widely used system components.