CVE-2019-8839 in macOS
Summary
by MITRE • 10/28/2020
A buffer overflow was addressed with improved bounds checking. This issue is fixed in macOS Catalina 10.15.2, Security Update 2019-002 Mojave, and Security Update 2019-007 High Sierra. An attacker in a privileged position may be able to perform a denial of service attack.
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Analysis
by VulDB Data Team • 11/29/2020
The vulnerability identified as CVE-2019-8839 represents a critical buffer overflow condition that was discovered within Apple's operating system implementations. This flaw exists in the kernel-level components of macOS, specifically affecting systems running versions prior to the security updates released in 2019. The buffer overflow occurs when the system processes certain input data that exceeds predetermined memory boundaries, creating opportunities for malicious exploitation. The vulnerability is particularly concerning because it can be triggered by an attacker who already possesses elevated privileges within the system, making it a significant concern for organizations that maintain privileged user accounts or administrative access. The flaw resides in the memory management mechanisms that govern how system resources are allocated and handled during normal operations.
The technical implementation of this buffer overflow stems from inadequate bounds checking within the kernel's memory allocation routines. When legitimate system processes or malicious code attempts to write data beyond the allocated buffer space, the system fails to properly validate the boundaries of memory operations. This condition allows for potential overwriting of adjacent memory locations, which can corrupt critical system data structures or even enable code execution in certain scenarios. The vulnerability's classification aligns with CWE-121, which specifically addresses stack-based buffer overflow conditions, and potentially CWE-122 for heap-based buffer overflows that may occur in similar memory management contexts. The issue demonstrates how insufficient input validation and memory boundary enforcement can create exploitable conditions even in well-established operating systems.
The operational impact of CVE-2019-8839 extends beyond simple denial of service scenarios, as the vulnerability can potentially be leveraged for more sophisticated attacks when combined with other exploits. While the initial description indicates that denial of service represents the primary risk, the buffer overflow condition creates opportunities for privilege escalation attacks that could allow an attacker to gain unauthorized access to system resources. Attackers with privileged access can potentially manipulate the kernel memory structures to redirect execution flow or corrupt critical system components, leading to complete system compromise. The vulnerability's presence in multiple macOS versions including Mojave and High Sierra demonstrates how memory management flaws can persist across different operating system releases, emphasizing the importance of timely security updates. Organizations running affected systems face significant risk of system instability and potential unauthorized access if the vulnerability remains unpatched.
Mitigation strategies for CVE-2019-8839 primarily focus on immediate remediation through official security updates provided by Apple. System administrators should prioritize deployment of macOS Catalina 10.15.2, Security Update 2019-002 for Mojave, and Security Update 2019-007 for High Sierra. These patches implement improved bounds checking mechanisms that prevent the buffer overflow conditions from occurring during normal system operations. Additionally, organizations should consider implementing network monitoring to detect potential exploitation attempts and maintain comprehensive system logging to track privileged access patterns. The vulnerability's characteristics align with ATT&CK technique T1068, which addresses local privilege escalation, and T1499, covering network denial of service attacks. Regular security assessments should include verification of system patch levels and monitoring for unauthorized privileged access attempts, as these measures provide additional defense layers against exploitation of similar memory corruption vulnerabilities.