CVE-2020-9899 in macOS
Summary
by MITRE • 10/23/2020
A memory corruption issue was addressed with improved input validation. This issue is fixed in macOS Catalina 10.15.6. An application may be able to execute arbitrary code with kernel privileges.
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Analysis
by VulDB Data Team • 10/03/2022
This vulnerability represents a critical memory corruption flaw that existed in Apple's macOS operating system, specifically affecting versions prior to Catalina 10.15.6. The issue stems from inadequate input validation mechanisms within the kernel components, creating a pathway for malicious applications to exploit memory handling inconsistencies. The vulnerability falls under the category of kernel-level memory corruption as defined by CWE-121, which encompasses buffer overflow conditions that can lead to privilege escalation. The flaw allows an attacker-controlled application to manipulate kernel memory structures in a manner that could result in arbitrary code execution with the highest system privileges. This represents a severe escalation of privileges vulnerability that directly undermines the operating system's security model and privilege separation mechanisms.
The technical exploitation of this vulnerability occurs when a malicious application provides crafted input to kernel APIs or system calls that do not properly validate the size or content of incoming data. When the kernel processes this malformed input, it can cause memory corruption that allows the attacker to overwrite critical kernel data structures or execute arbitrary code within the kernel context. This type of vulnerability is particularly dangerous because it operates at the kernel level where all system protections are effectively bypassed. The exploitation technique aligns with ATT&CK tactics involving privilege escalation and defense evasion, as the attacker can gain root-level access to the system and potentially hide their activities from normal security monitoring mechanisms. The vulnerability demonstrates how insufficient input validation can create attack vectors that directly compromise the integrity of the operating system's core security features.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it enables attackers to gain complete control over affected systems. Once successfully exploited, an attacker can install persistent backdoors, modify system files, access all user data, and potentially use the compromised system as a launch point for further attacks within a network environment. The vulnerability affects all macOS versions prior to 10.15.6, making it particularly concerning for organizations that have not yet updated their systems. From a security operations perspective, this vulnerability represents a high-priority threat that requires immediate remediation, as it provides attackers with the capability to achieve complete system compromise without requiring additional attack vectors. The memory corruption nature of the vulnerability means that exploitation could potentially lead to system crashes or instability, which attackers might use to their advantage for denial-of-service attacks or to cover their tracks.
Organizations should prioritize immediate patching of macOS systems to address this vulnerability, as the risk of exploitation remains high for unpatched systems. Apple's release of macOS Catalina 10.15.6 included specific mitigations that address the input validation gaps, and system administrators should ensure all endpoints are updated to this or later versions. Additional mitigations include implementing application whitelisting policies to prevent unauthorized applications from running, monitoring for suspicious kernel activity, and conducting regular security assessments of macOS environments. The vulnerability highlights the importance of maintaining up-to-date operating system versions and implementing comprehensive patch management processes. Security teams should also consider deploying kernel integrity monitoring solutions that can detect anomalous kernel behavior indicative of exploitation attempts, as traditional endpoint protection solutions may not adequately detect kernel-level attacks that bypass user-mode security controls.