CVE-2020-29622 in macOS
Summary
by MITRE • 10/19/2021
A race condition was addressed with additional validation. This issue is fixed in Security Update 2021-005 Catalina. Mounting a maliciously crafted NFS network share may lead to arbitrary code execution with system privileges.
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Analysis
by VulDB Data Team • 10/23/2021
The vulnerability identified as CVE-2020-29622 represents a critical race condition flaw within the macOS operating system that was resolved through Security Update 2021-005 for Catalina. This race condition specifically affects the Network File System (NFS) implementation and occurs during the process of mounting network shares. The flaw arises from insufficient validation mechanisms that allow malicious actors to exploit temporal gaps in the system's processing of NFS mount requests, creating opportunities for privilege escalation and arbitrary code execution.
The technical nature of this vulnerability aligns with CWE-362, which describes race conditions in software systems where concurrent operations can lead to unpredictable behavior and security exploits. The flaw manifests when a maliciously crafted NFS share is mounted on a vulnerable system, allowing attackers to manipulate the timing of system calls and file operations to execute code with system-level privileges. This race condition occurs during the NFS mount process where the system fails to properly validate the integrity of the share before establishing the connection, creating a window of opportunity for attackers to inject malicious code or manipulate the system's behavior.
From an operational impact perspective, this vulnerability presents a significant threat to macOS environments as it allows remote attackers to gain complete system control without requiring user interaction or authentication. The exploit requires only the ability to create or access a malicious NFS share, making it particularly dangerous in networked environments where users may inadvertently mount shares from untrusted sources. The arbitrary code execution capability means that attackers can install malware, modify system files, establish backdoors, or extract sensitive data from compromised systems. This vulnerability affects the fundamental security model of macOS, as it allows privilege escalation from standard user level to system administrator level without proper authentication mechanisms.
The mitigation strategy for CVE-2020-29622 involves applying the Security Update 2021-005 for macOS Catalina, which addresses the race condition through enhanced validation mechanisms and improved synchronization controls during NFS mount operations. Organizations should also implement network segmentation to limit access to NFS shares, disable unnecessary NFS services, and monitor for suspicious mount activities. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence, specifically T1068 for local privilege escalation and T1078 for valid accounts. System administrators should also consider implementing network monitoring solutions to detect anomalous NFS mount behavior and establish baseline network activities to identify potential exploitation attempts. The fix implemented in the security update includes additional input validation and improved race condition handling mechanisms that prevent the exploitation path by ensuring proper synchronization between system operations during NFS share mounting processes.