CVE-2021-0481 in Android
Summary
by MITRE • 06/11/2021
In onActivityResult of EditUserPhotoController.java, there is a possible access of unauthorized files due to an unexpected URI handler. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is needed for exploitation.Product: AndroidVersions: Android-8.1 Android-9 Android-10 Android-11Android ID: A-172939189
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-0481 resides within the onActivityResult method of the EditUserPhotoController.java component in Android operating systems spanning versions 8.1 through 11. This flaw represents a critical security weakness that stems from improper handling of URI schemes within the Android framework's file access mechanisms. The vulnerability manifests when the application processes user-provided URI references during photo editing operations, creating an unexpected pathway for unauthorized file access. The issue falls under the category of privilege escalation vulnerabilities, specifically enabling local escalation of privilege without requiring additional execution privileges or elevated user rights. The attack vector requires user interaction, meaning an attacker must convince a victim to perform a specific action such as selecting a malicious file through the photo editing interface. This type of vulnerability is particularly concerning as it leverages legitimate application functionality to bypass normal access controls that should protect sensitive system resources. The root cause can be traced to inadequate validation of URI parameters and insufficient sandboxing of file access operations within the application's onActivityResult handler.
The technical implementation of this vulnerability exploits the Android system's content provider framework and URI resolution mechanisms. When a user interacts with the photo editing interface, the application's onActivityResult method processes incoming URI references without proper sanitization or access control verification. This allows an attacker to craft malicious URI schemes that can traverse the file system beyond intended boundaries, potentially accessing sensitive files that should be restricted to specific applications or system components. The vulnerability demonstrates characteristics consistent with CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-73, which covers external control of file name or path. The flaw essentially creates a path traversal condition within the application's file access logic, enabling unauthorized file system access through what should be a controlled user interface element. The Android system's permission model is effectively bypassed through this URI manipulation technique, allowing the application to access files that it would normally not have access to based on its declared permissions.
From an operational perspective, this vulnerability poses significant risks to Android device security and user privacy. The local escalation of privilege capability means that an attacker could potentially access sensitive user data, system configuration files, or other protected resources that are normally restricted to system-level processes or specific applications. The requirement for user interaction makes this vulnerability exploitable through social engineering attacks where victims are tricked into selecting malicious files through the photo editing interface. This attack scenario aligns with ATT&CK technique T1059, which involves executing malicious code through legitimate system interfaces, and T1068, which describes local privilege escalation through system-level vulnerabilities. The impact extends beyond simple data access, as the attacker could potentially modify system files, install malicious components, or escalate privileges to gain full system control. The vulnerability affects all Android versions mentioned, indicating a widespread exposure that spans multiple generations of the platform, making it particularly dangerous for organizations and users who have not yet updated their systems.
Mitigation strategies for CVE-2021-0481 should focus on both immediate patching and defensive programming practices. The primary solution involves applying the official Android security patches released by Google to address the URI handling vulnerability in the onActivityResult method. Organizations should implement strict input validation for all URI parameters received through the content provider framework, ensuring that file paths are properly sanitized and validated before any file access operations are performed. Developers should adopt secure coding practices that include implementing proper access controls, using whitelisting approaches for URI schemes, and avoiding direct URI parameter usage without comprehensive validation. The fix should involve implementing robust URI parsing and validation logic that prevents path traversal attacks and ensures that all file access operations occur within designated safe directories. Additionally, application developers should consider implementing additional security layers such as file access logging, monitoring for unusual file access patterns, and regular security code reviews focused on URI handling components. Organizations should also implement network monitoring to detect potential exploitation attempts and establish incident response procedures specifically designed to address local privilege escalation vulnerabilities in mobile applications.