CVE-2020-9900 in watchOS
Summary
by MITRE • 10/23/2020
An issue existed within the path validation logic for symlinks. This issue was addressed with improved path sanitization. This issue is fixed in iOS 13.6 and iPadOS 13.6, macOS Catalina 10.15.6, tvOS 13.4.8, watchOS 6.2.8. A local attacker may be able to elevate their privileges.
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Analysis
by VulDB Data Team • 10/03/2022
The vulnerability identified as CVE-2020-9900 represents a critical path validation flaw within Apple's operating systems that specifically affects symbolic link handling mechanisms. This issue resides in the core file system traversal logic where the system fails to properly sanitize and validate paths when processing symbolic links, creating a potential privilege escalation vector for local attackers. The vulnerability impacts multiple Apple platforms including iOS, iPadOS, macOS, tvOS, and watchOS, indicating a systemic issue within the operating system's path resolution architecture that requires comprehensive remediation across the entire ecosystem.
The technical flaw stems from inadequate input validation during symbolic link resolution processes where the system does not sufficiently sanitize path components before traversing directory structures. This path validation weakness allows an attacker to craft malicious symbolic link sequences that can bypass normal access controls and directory boundaries. The vulnerability specifically manifests when the system processes symbolic links that contain specially crafted path components or sequences that could lead to unexpected directory traversal behavior. According to CWE classification, this vulnerability maps to CWE-22 Path Traversal, which encompasses improper handling of directory traversal sequences in file system operations. The issue demonstrates characteristics of CWE-78 Path Traversal in Command - a category that includes vulnerabilities where user-supplied input is used to construct file paths without proper sanitization, leading to unauthorized access to system resources.
The operational impact of this vulnerability is significant as it provides local attackers with a means to elevate their privileges within the operating system environment. While the vulnerability requires local system access to exploit, the privilege escalation capability makes it particularly dangerous in scenarios where attackers can obtain user-level access through other means. The fix implemented by Apple addresses the core path sanitization logic that governs how symbolic links are processed, ensuring that path components are properly validated and normalized before any directory traversal operations occur. This remediation directly addresses the root cause by implementing stricter path validation checks that prevent malicious path sequences from being processed through the system's symbolic link resolution mechanisms. The vulnerability affects the fundamental file system security model of Apple's platforms, potentially allowing attackers to access restricted files, directories, or system resources that should normally be protected from unauthorized access.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and specifically addresses path traversal attacks that can be leveraged to gain elevated system privileges. The mitigation strategy requires immediate deployment of the patched versions across all affected Apple platforms, with particular attention to ensuring that all system components are updated to the latest security releases. Organizations should conduct thorough vulnerability assessments to identify systems running affected versions of the operating systems and prioritize remediation efforts accordingly. The fix demonstrates Apple's approach to addressing file system security issues through enhanced input validation and sanitization, which aligns with industry best practices for preventing path traversal attacks and maintaining system integrity. Regular security monitoring and patch management procedures should be reinforced to prevent similar vulnerabilities from emerging in the future, particularly focusing on the validation of file system operations and symbolic link handling within mobile and desktop operating environments.