CVE-2016-4688 in watchOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.1 is affected. macOS before 10.12.1 is affected. tvOS before 10.0.1 is affected. watchOS before 3.1 is affected. watchOS before 3.1.3 is affected. The issue involves the "FontParser" component. It allows remote attackers to execute arbitrary code or cause a denial of service (buffer overflow and application crash) via a crafted font.
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Analysis
by VulDB Data Team • 09/20/2024
The vulnerability identified as CVE-2016-4688 represents a critical buffer overflow flaw within Apple's FontParser component that affects multiple operating systems including iOS, macOS, tvOS, and watchOS. This issue stems from inadequate input validation when processing specially crafted font files, creating a pathway for remote attackers to exploit the system through maliciously constructed font content. The vulnerability specifically impacts iOS versions prior to 10.1, macOS versions before 10.12.1, tvOS versions before 10.0.1, and watchOS versions before 3.1 and 3.1.3 respectively, highlighting the widespread nature of the affected platforms. The FontParser component serves as a fundamental system element responsible for interpreting and rendering font data across Apple's ecosystem, making it a prime target for exploitation given its widespread usage in displaying text content.
The technical exploitation of this vulnerability occurs through buffer overflow conditions that arise when the FontParser component processes malformed font files containing oversized data structures or improperly formatted font metrics. Attackers can craft malicious font files that, when processed by the vulnerable system, cause memory corruption leading to arbitrary code execution or application crashes. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of how improper bounds checking in parsing routines can create security risks. The buffer overflow occurs at the point where font data is parsed and loaded into memory, typically during font rendering operations when the system attempts to interpret font metrics, glyph data, or other font-specific metadata. The exploitation mechanism leverages the fact that the FontParser does not properly validate the size and structure of font data before attempting to load it into fixed-size memory buffers.
The operational impact of this vulnerability extends beyond simple application crashes to potentially enable full system compromise through remote code execution. When an attacker successfully exploits this vulnerability, they can execute arbitrary code with the privileges of the affected application, potentially leading to complete system compromise depending on the context in which the font parsing occurs. The vulnerability affects not just individual applications but the underlying system font rendering infrastructure, making it particularly dangerous as it can be triggered through various attack vectors including email attachments, web content, or downloaded font files. This type of attack aligns with ATT&CK technique T1059.007, which covers the use of scripting languages for execution, as attackers can leverage the font parsing infrastructure to execute malicious code within the system context. The vulnerability's remote nature means that exploitation can occur without physical access to the device, making it particularly concerning for mobile and embedded systems where users may unknowingly encounter malicious font content.
The mitigation strategy for CVE-2016-4688 requires immediate deployment of Apple's security updates and patches addressing the FontParser component vulnerabilities. System administrators should prioritize updating all affected Apple platforms to their respective patched versions, with particular attention to iOS 10.1, macOS 10.12.1, tvOS 10.0.1, and watchOS 3.1.3 releases. Organizations should implement network-level controls to prevent the delivery of potentially malicious font files through email attachments, web downloads, or other vectors where font content might be processed. The vulnerability demonstrates the importance of input validation and bounds checking in system components that process untrusted data, reinforcing industry best practices outlined in the OWASP Top Ten and other security frameworks. Additionally, implementing sandboxing mechanisms and privilege separation for font processing components can help limit the impact of potential exploitation attempts, while regular security assessments of system components can help identify similar vulnerabilities in other parsing routines.