CVE-2020-36615 in macOS
Summary
by MITRE • 08/15/2023
An out-of-bounds read was addressed with improved bounds checking. This issue is fixed in macOS Big Sur 11.0.1. Processing a maliciously crafted font may lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 08/15/2023
This vulnerability represents a critical out-of-bounds read condition that was successfully addressed through enhanced bounds checking mechanisms within the macOS Big Sur 11.0.1 update. The flaw specifically manifests when the system processes font files that have been maliciously crafted to exploit memory access violations. From a technical perspective, this issue falls under the common weakness enumeration CWE-129 which categorizes improper bounds checking vulnerabilities that can lead to memory corruption and potential code execution. The vulnerability operates at the intersection of font processing and memory management, where insufficient validation of font data structures allows attackers to manipulate memory access patterns beyond allocated boundaries.
The operational impact of this vulnerability extends beyond simple memory corruption, as it provides a pathway for arbitrary code execution when legitimate applications process malicious font files. This represents a significant security risk because font rendering is a common operation across multiple system components and applications, making the attack surface particularly broad. The vulnerability's exploitation potential aligns with ATT&CK technique T1059.007 which describes execution through scripting languages, as font processing often involves interpreted code paths that can be manipulated to execute malicious payloads. Attackers could potentially deliver malicious fonts through various vectors including email attachments, web downloads, or compromised applications that render text using affected font processing libraries.
The fix implemented in macOS Big Sur 11.0.1 demonstrates proper defensive programming practices through enhanced input validation and bounds checking mechanisms. This remediation addresses the root cause by ensuring that all font data is properly validated before memory access operations occur, preventing unauthorized memory reads that could expose sensitive data or enable privilege escalation. The update specifically targets the font rendering subsystem where the vulnerability was identified, suggesting that the fix involves modifications to how the system parses and processes font file structures including TrueType, OpenType, and other font formats. Organizations should prioritize deployment of this update as it represents a critical security measure that directly addresses a known exploit vector for remote code execution attacks. The vulnerability's classification as a memory safety issue underscores the importance of proper bounds checking in system libraries that handle untrusted input data, particularly in graphics and font processing components that are frequently accessed by user applications and system services.