CVE-2015-6985 in Mac OS X
Summary
by MITRE
Apple Type Services (ATS) in Apple OS X before 10.11.1 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a crafted web page.
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Analysis
by VulDB Data Team • 06/24/2022
Apple Type Services represents a critical component within Apple's operating system architecture responsible for handling font rendering and text processing operations across various applications and web content. This subsystem operates at a low level within the system kernel, processing font data and text formatting instructions that are essential for user interface elements, document rendering, and web page display functionality. The vulnerability exists within the ATS implementation where insufficient input validation occurs when processing specially crafted font files or text formatting data embedded within web pages. Attackers can exploit this weakness by embedding malicious font data or malformed text structures within web content that triggers memory corruption during the font processing routine. The flaw specifically manifests when the ATS subsystem attempts to parse and render crafted font files that contain oversized or malformed data structures that exceed buffer boundaries or corrupt memory allocations within the processing pipeline.
The technical exploitation of CVE-2015-6985 demonstrates a classic memory corruption vulnerability that operates through the manipulation of font rendering processes. When a web browser or application processes a maliciously crafted web page containing specially designed font data, the ATS subsystem attempts to allocate memory buffers to handle the font information. However, the vulnerable implementation fails to properly validate the size and structure of incoming font data, allowing attackers to overflow memory buffers or corrupt heap allocations. This memory corruption can result in arbitrary code execution when the corrupted memory is subsequently accessed during normal processing operations, or cause application crashes and system instability when the memory corruption leads to segmentation faults or access violations. The vulnerability affects the core operating system functionality and can be triggered through multiple attack vectors including web browsing, email rendering, and document processing activities that utilize font rendering capabilities.
The operational impact of this vulnerability extends beyond simple denial of service conditions to represent a significant security risk that could enable full system compromise. Remote attackers can leverage this vulnerability to execute malicious code with the privileges of the affected application, potentially leading to complete system takeover. The memory corruption issues can cause unpredictable behavior including application crashes, system instability, and potential privilege escalation opportunities. Organizations relying on Apple operating systems face substantial risk exposure as this vulnerability can be exploited through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website. The vulnerability affects a broad range of applications that depend on ATS for text rendering, including Safari web browser, Mail application, and various third-party applications that utilize the system's font processing capabilities. This makes the attack surface particularly wide and difficult to fully mitigate through application-specific patches alone.
Mitigation strategies for CVE-2015-6985 require immediate system updates and comprehensive security measures to protect against exploitation attempts. Apple released OS X 10.11.1 and subsequent updates that address the memory corruption issues within ATS by implementing proper input validation and buffer boundary checks. Security administrators should prioritize deployment of these patches across all affected systems and monitor for potential exploitation attempts. Additional protective measures include implementing web content filtering solutions, disabling unnecessary font rendering capabilities in web browsers, and employing network-based intrusion detection systems to identify potential exploitation attempts. The vulnerability aligns with CWE-121, heap-based buffer overflow, and CWE-125, out-of-bounds read, and maps to ATT&CK technique T1059.007 for command and scripting interpreter. Organizations should also consider implementing application whitelisting policies and sandboxing mechanisms to limit the potential impact of successful exploitation attempts, particularly in enterprise environments where system integrity is paramount for maintaining operational security.