CVE-2020-3855 in macOS
Summary
by MITRE • 10/28/2020
An access issue was addressed with improved access restrictions. This issue is fixed in macOS Catalina 10.15.3, Security Update 2020-001 Mojave, Security Update 2020-001 High Sierra. A malicious application may be able to overwrite arbitrary files.
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Analysis
by VulDB Data Team • 04/06/2024
This vulnerability represents a critical access control flaw that existed in Apple's macOS operating system across multiple versions including Catalina 10.15.3, Mojave Security Update 2020-001, and High Sierra Security Update 2020-001. The issue stems from insufficient access restrictions that allowed unauthorized applications to manipulate system files through improper privilege escalation mechanisms. The vulnerability falls under the category of improper access control as defined by CWE-284, which specifically addresses inadequate access control measures that permit unauthorized access to resources or capabilities. From an operational perspective, this flaw creates a significant attack surface where malicious actors could potentially overwrite arbitrary files on affected systems, compromising system integrity and potentially leading to complete system compromise.
The technical implementation of this vulnerability likely involves a race condition or privilege escalation mechanism where applications can bypass normal file system access controls. Attackers could exploit this weakness by crafting malicious applications that leverage the improper access restrictions to target system files or user data. The vulnerability's impact is particularly severe because it allows for arbitrary file overwrites, which could be used to modify system binaries, configuration files, or user data, potentially enabling persistent access or denial of service conditions. This type of flaw aligns with ATT&CK technique T1059 which covers executing malicious code through various system interfaces, and T1070 which involves clearing event logs and other system artifacts to maintain persistence.
The remediation approach for this vulnerability involves applying the respective security updates provided by Apple, specifically the Security Update 2020-001 for affected macOS versions. System administrators should prioritize deployment of these patches across all affected endpoints and verify successful installation through automated compliance monitoring tools. Organizations should also implement additional security controls such as application whitelisting, sandboxing mechanisms, and regular security assessments to reduce the risk of exploitation. The fix likely addresses the root cause through enhanced kernel-level access control checks that properly validate application privileges before allowing file system modifications. This vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how seemingly minor access control flaws can create significant security risks in operating system environments.