CVE-2020-3830 in macOS
Summary
by MITRE
A validation issue existed in the handling of symlinks. This issue was addressed with improved validation of symlinks. This issue is fixed in macOS Catalina 10.15.3. A malicious application may be able to overwrite arbitrary files.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/06/2024
The vulnerability identified as CVE-2020-3830 represents a critical symlink validation flaw that existed in macOS operating systems prior to version 10.15.3. This issue stems from inadequate handling of symbolic links during file operations, creating a pathway for malicious applications to exploit the system's file management mechanisms. The vulnerability specifically targets the validation process that should occur when processing symbolic links, allowing attackers to manipulate file system operations in unintended ways.
The technical flaw manifests in the insufficient validation checks applied to symbolic link operations within the macOS file system. When applications process symbolic links, the system should verify that these links point to legitimate destinations and that the operations being performed do not create opportunities for privilege escalation or arbitrary file overwrites. However, the validation mechanism failed to properly examine the integrity and legitimacy of symlink targets, particularly in scenarios where applications might be processing user-supplied or untrusted symbolic links. This weakness allows an attacker to craft malicious symlink structures that bypass normal security checks.
The operational impact of this vulnerability is significant as it enables a malicious application to overwrite arbitrary files on the system. Attackers can exploit this flaw by creating carefully constructed symbolic links that, when processed by vulnerable applications, redirect file operations to unintended destinations. This capability can be leveraged to overwrite critical system files, configuration files, or user data, potentially leading to system compromise, data loss, or privilege escalation. The vulnerability essentially allows attackers to perform unauthorized file modifications without proper system permissions, undermining the fundamental security model of macOS file system access controls.
The fix implemented in macOS Catalina 10.15.3 addresses this issue through enhanced validation of symbolic link operations. This improvement involves strengthening the checks that occur when symbolic links are processed, ensuring that all link targets are properly validated before any file operations are executed. The update implements stricter verification mechanisms that prevent malicious applications from exploiting the symlink handling process to overwrite files outside of their intended scope.
From a cybersecurity perspective, this vulnerability aligns with CWE-59 and CWE-22 categories, representing weaknesses in file path handling and symbolic link validation. The attack surface described in the ATT&CK framework would fall under the T1059.007 technique for "Command and Scripting Interpreter: PowerShell" or similar execution methods that leverage file system manipulation. Organizations should prioritize updating to macOS 10.15.3 or later versions to remediate this vulnerability, while also implementing monitoring for suspicious symlink creation patterns and file overwrite activities that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation and the potential for seemingly minor file system flaws to enable significant security breaches.