CVE-2020-3893 in macOS
Summary
by MITRE
A memory corruption issue was addressed with improved input validation. This issue is fixed in macOS Catalina 10.15.4. A malicious application may be able to execute arbitrary code with kernel privileges.
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Analysis
by VulDB Data Team • 10/06/2020
This vulnerability represents a critical memory corruption flaw that existed within the macOS kernel implementation, specifically affecting versions prior to 10.15.4. The issue stems from inadequate input validation mechanisms that allowed malicious applications to exploit memory handling routines and potentially escalate privileges to kernel level access. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, though the specific implementation likely involved more complex memory corruption patterns that could be leveraged for privilege escalation. Attackers could craft malicious applications that would trigger the memory corruption during normal execution flows, potentially leading to arbitrary code execution with the highest system privileges. This represents a severe security weakness in the kernel's memory management subsystem where proper bounds checking and input sanitization were insufficient to prevent malicious data from corrupting kernel memory structures. The vulnerability demonstrates a failure in the principle of least privilege and proper memory isolation within the operating system's security architecture, creating an attack surface where user-mode applications could potentially compromise the entire system kernel.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally undermines the security model of macOS by allowing malicious code to operate at the kernel level where it can bypass all user-space protections. This creates a persistent threat vector that could enable attackers to install rootkits, modify system files, monitor user activities, and establish persistent backdoors within the operating system. The exploitation process would likely involve careful crafting of input data that when processed by the vulnerable kernel routines would overwrite critical memory locations, potentially including return addresses, function pointers, or other control structures within kernel memory. This type of vulnerability is particularly dangerous because kernel-level access provides complete system control, including the ability to manipulate all running processes, access encrypted data, and disable security features. The attack surface is limited to applications that can be executed on the target system, but the consequences are severe enough that any successful exploitation could result in complete system compromise.
Mitigation strategies for this vulnerability must address both the immediate patching requirement and broader security hardening measures. The primary fix involves updating to macOS Catalina 10.15.4 or later versions where improved input validation mechanisms have been implemented to prevent the memory corruption patterns that enabled exploitation. Organizations should implement comprehensive patch management processes to ensure all systems receive the security updates promptly, as this vulnerability could be exploited in zero-day scenarios before public disclosure. Additional protective measures include implementing application whitelisting policies, enabling system integrity protection features, and monitoring for unusual kernel-level activity that might indicate exploitation attempts. Security teams should also consider deploying endpoint detection and response solutions that can monitor for suspicious kernel-mode behavior and anomalous system calls that might indicate exploitation of similar memory corruption vulnerabilities. The vulnerability highlights the importance of robust input validation and memory safety practices in kernel development, aligning with ATT&CK technique T1068 which covers local privilege escalation through kernel exploits, and emphasizing the need for defense-in-depth strategies that protect against both known and unknown vulnerabilities through multiple layers of security controls.