CVE-2020-9930 in macOS
Summary
by MITRE • 04/03/2021
An out-of-bounds read was addressed with improved input validation. This issue is fixed in macOS Catalina 10.15.6, Security Update 2020-004 Mojave, Security Update 2020-004 High Sierra. A local user may be able to cause unexpected system termination or read kernel memory.
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Analysis
by VulDB Data Team • 04/08/2021
The vulnerability identified as CVE-2020-9930 represents a critical out-of-bounds read flaw within Apple's macOS operating system that was addressed through enhanced input validation mechanisms. This issue affected multiple versions of macOS including Catalina 10.15.6, Mojave Security Update 2020-004, and High Sierra Security Update 2020-004. The flaw resides in the kernel-level processing of input data where insufficient validation allows malicious actors to exploit memory access patterns that could lead to system instability. From a cybersecurity perspective, this vulnerability falls under the CWE-125 weakness category, which specifically addresses out-of-bounds read conditions that can result in information disclosure or system compromise.
The technical implementation of this vulnerability stems from inadequate bounds checking within kernel memory management routines that process user-supplied data. When legitimate system processes encounter malformed or oversized input parameters, the kernel's memory access controls fail to properly validate the boundaries of memory regions being accessed. This allows an attacker to manipulate memory access patterns that extend beyond allocated buffer boundaries, potentially causing system crashes or enabling unauthorized memory reads. The flaw operates at the kernel level, making it particularly dangerous as it can bypass standard user-space protections and directly access sensitive kernel memory regions. This type of vulnerability is classified under the ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and specifically addresses kernel exploits that leverage memory corruption weaknesses.
The operational impact of CVE-2020-9930 extends beyond simple system instability to encompass potential information disclosure and unauthorized access to kernel memory spaces. A local user with minimal privileges could exploit this vulnerability to cause unexpected system termination, which may be leveraged as a denial-of-service vector, or to read sensitive kernel memory contents that could reveal system configuration details, encryption keys, or other confidential information. The vulnerability's exploitation requires local system access, but the potential for privilege escalation remains significant given the kernel-level nature of the flaw. Attackers could potentially use this vulnerability as a stepping stone for more sophisticated attacks, particularly when combined with other exploits that may be available on the same system. The security implications are further amplified by the fact that kernel memory reads could expose sensitive data structures that might reveal system internals or authentication mechanisms.
Mitigation strategies for CVE-2020-9930 primarily focus on applying the official security updates released by Apple for the affected macOS versions. System administrators should prioritize deployment of Security Update 2020-004 for Mojave and High Sierra systems, along with upgrading to macOS Catalina 10.15.6 for affected systems. Additional protective measures include implementing strict access controls to limit local user privileges, monitoring system logs for unusual termination patterns, and employing kernel integrity protection mechanisms such as System Integrity Protection. Network administrators should also consider implementing endpoint detection and response solutions that can monitor for anomalous memory access patterns or system stability issues that might indicate exploitation attempts. The vulnerability's resolution through improved input validation aligns with industry best practices for preventing memory safety issues and demonstrates Apple's commitment to addressing kernel-level security concerns through proactive patch management and code review processes.