CVE-2016-4691 in watchOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.2 is affected. macOS before 10.12.2 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 (memory corruption and application crash) via a crafted font.
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Analysis
by VulDB Data Team • 09/20/2024
The vulnerability identified as CVE-2016-4691 represents a critical memory corruption flaw within Apple's FontParser component that affects multiple operating systems including iOS versions prior to 10.2, macOS versions before 10.12.2, and watchOS versions before 3.1.3. This issue demonstrates the inherent risks associated with font parsing libraries, which are commonly targeted by attackers due to their frequent use in rendering text across various applications and system components. The vulnerability resides in how the FontParser handles malformed font files, specifically within the processing of font table structures that can lead to improper memory management and subsequent code execution or system instability.
The technical nature of this flaw stems from insufficient input validation and memory management within the font parsing mechanism. When a maliciously crafted font file is processed by the FontParser component, the vulnerability manifests through buffer overflows or improper memory deallocation that can be exploited to overwrite critical memory locations. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. Attackers can leverage this weakness by embedding malicious font content in various file formats such as pdf documents, image files, or web content that will trigger the font parsing process when displayed or rendered by affected applications.
The operational impact of CVE-2016-4691 extends beyond simple denial of service conditions to encompass full remote code execution capabilities that can compromise entire systems. When exploited, this vulnerability allows attackers to execute arbitrary code with the privileges of the affected application, potentially leading to complete system compromise. The attack surface is particularly broad since font files are commonly encountered in email attachments, web browsing sessions, document processing, and multimedia content across all affected Apple platforms. This vulnerability directly maps to ATT&CK technique T1059.007, which covers scripting through webshell, and T1203, which involves exploitation for privilege escalation, as the initial compromise can lead to broader system access.
Mitigation strategies for this vulnerability require immediate system updates to the patched versions of iOS, macOS, and watchOS where Apple has addressed the underlying memory corruption issues in the FontParser component. Organizations should implement proactive measures including network segmentation, email filtering, and web content restrictions to prevent the delivery of potentially malicious font files. Additionally, security teams should monitor for indicators of compromise related to suspicious font file handling and implement application whitelisting where possible to restrict the execution of untrusted font rendering components. The remediation process must also include thorough testing of patched systems to ensure that the vulnerability has been properly addressed without introducing regressions in font rendering functionality across the affected platforms.