CVE-2020-9859 in macOS
Summary
by MITRE
A memory consumption issue was addressed with improved memory handling. This issue is fixed in iOS 13.5.1 and iPadOS 13.5.1, macOS Catalina 10.15.5 Supplemental Update, tvOS 13.4.6, watchOS 6.2.6. An application may be able to execute arbitrary code with kernel privileges.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/29/2025
The vulnerability identified as CVE-2020-9859 represents a critical memory consumption flaw that was remediated through enhanced memory management protocols in several Apple operating system versions. This issue falls under the category of memory management vulnerabilities that can potentially lead to privilege escalation and arbitrary code execution. The flaw existed in the kernel-level memory handling mechanisms of Apple's operating systems, creating a potential attack surface that malicious applications could exploit to gain elevated privileges.
The technical nature of this vulnerability stems from inadequate memory handling procedures within the kernel components of Apple's operating systems. When applications attempt to consume memory resources in specific patterns or sequences, the system's memory management subsystem fails to properly validate or restrict these operations. This improper memory handling creates conditions where an application can manipulate kernel memory structures to execute arbitrary code with the highest privileges available to the system. The vulnerability is particularly concerning because it operates at the kernel level, where applications have the most extensive system access and control capabilities.
The operational impact of CVE-2020-9859 extends beyond simple memory exhaustion scenarios. Attackers who successfully exploit this vulnerability can potentially achieve complete system compromise by executing malicious code with kernel privileges. This level of access enables adversaries to bypass standard security controls, modify system files, install persistent backdoors, and access sensitive data without detection. The risk is amplified by the fact that the vulnerability affects multiple Apple platforms including iOS, iPadOS, macOS, tvOS, and watchOS, creating a widespread attack surface that could impact millions of devices simultaneously. This cross-platform nature aligns with ATT&CK technique T1068 which describes local privilege escalation through kernel exploits.
The remediation for this vulnerability required Apple to implement enhanced memory validation checks and improved memory allocation procedures within their kernel components. The fixes were rolled out through specific software updates including iOS 13.5.1, iPadOS 13.5.1, macOS Catalina 10.15.5 Supplemental Update, tvOS 13.4.6, and watchOS 6.2.6. These updates address the root cause by strengthening the memory management subsystem to properly validate memory allocation requests and prevent malicious applications from manipulating kernel memory structures. The solution follows established security principles that align with CWE-129 which addresses improper validation of array indices and memory access violations in kernel-level code.
Organizations and users should prioritize immediate deployment of these security updates to mitigate the risk of exploitation. The vulnerability represents a significant threat to system integrity and data security, particularly in environments where Apple devices are used for sensitive operations. Security teams should also implement monitoring for unusual memory consumption patterns or suspicious application behavior that might indicate exploitation attempts. The fix demonstrates Apple's ongoing commitment to addressing kernel-level security issues and maintaining system integrity across their ecosystem of devices. This vulnerability serves as a reminder of the critical importance of kernel security and proper memory management in preventing privilege escalation attacks that could compromise entire computing environments.