CVE-2016-1797 in Mac OS X
Summary
by MITRE
Apple Type Services (ATS) in Apple OS X before 10.11.5 allows attackers to bypass intended FontValidator sandbox-policy restrictions and execute arbitrary code in a privileged context via a crafted app.
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Analysis
by VulDB Data Team • 08/19/2022
Apple Type Services represents a critical component within macOS responsible for font handling and rendering operations across the operating system. The vulnerability CVE-2016-1797 specifically targets the FontValidator functionality within ATS, which operates under strict sandboxing policies designed to prevent unauthorized code execution. This flaw exists in Apple OS X versions prior to 10.11.5 and allows malicious actors to circumvent the intended security boundaries that normally restrict font processing operations to prevent privilege escalation attacks.
The technical implementation of this vulnerability stems from insufficient input validation within the font processing pipeline of Apple Type Services. Attackers can craft specially designed malicious font files that exploit a flaw in the validation mechanism, enabling them to execute arbitrary code with elevated privileges typically reserved for system-level processes. This represents a classic sandbox escape vulnerability where the boundary protection mechanisms fail to properly contain the font processing operations. The vulnerability operates at the kernel level within the ATS framework, allowing attackers to bypass the standard privilege separation that normally prevents user-space applications from executing code with system privileges.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the ability to gain unauthorized access to system resources and potentially escalate their privileges to root level access. This type of vulnerability falls under the CWE-248 category of "Uncaught Exception" and aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation." The attack vector requires a crafted application or font file that triggers the vulnerable code path within ATS, making it particularly dangerous as it can be delivered through seemingly legitimate font installations or applications that process font data.
Organizations and users affected by this vulnerability should immediately apply the security patches released by Apple as part of macOS 10.11.5 update. The mitigation strategy involves not only patching the operating system but also implementing additional monitoring for suspicious font processing activities and reviewing system logs for potential exploitation attempts. Security teams should also consider implementing application whitelisting policies that restrict font processing operations to trusted sources only, while maintaining network-based detection capabilities to identify potential exploitation attempts through network traffic analysis. The vulnerability demonstrates the critical importance of proper sandbox implementation and input validation in system-level components that handle untrusted data, as even seemingly benign operations like font rendering can become attack vectors when proper security boundaries are not maintained.