CVE-2021-39643 in Android
Summary
by MITRE • 12/15/2021
In ic_startRetrieveEntryValue of acropora/app/identity/ic.c, there is a possible bypass of defense-in-depth due to missing validation of the return value. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-195573629References: N/A
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-39643 resides within the Android kernel's identity management subsystem, specifically in the ic_startRetrieveEntryValue function located in acropora/app/identity/ic.c. This flaw represents a critical security weakness that undermines the system's defense-in-depth mechanisms through inadequate input validation. The issue manifests when the function fails to properly validate the return value from a critical operation, creating a potential pathway for malicious actors to circumvent security controls that should normally prevent unauthorized access to privileged system resources.
The technical implementation of this vulnerability stems from a missing validation check that should occur after a system call or function execution within the identity management framework. When the ic_startRetrieveEntryValue function executes without proper validation of its return value, it allows for potential manipulation of the control flow or data processing within the authentication and authorization mechanisms. This absence of validation creates a condition where an attacker could potentially exploit the function's behavior to bypass normal access controls that would typically restrict privilege escalation. The vulnerability specifically affects Android kernel implementations where the identity management system is responsible for handling credential retrieval and validation processes.
The operational impact of this vulnerability is severe as it enables local privilege escalation to system-level privileges without requiring any user interaction for exploitation. This means that an attacker with local access to an Android device could potentially elevate their privileges from standard user level to system level, gaining complete control over the device's functionality. The implications extend beyond simple privilege escalation as this could allow for complete system compromise, enabling unauthorized access to sensitive data, modification of system files, and potential persistence mechanisms. The vulnerability's local nature makes it particularly dangerous in environments where physical access to devices is possible, as it could be exploited by malware or malicious applications already present on the device.
The security implications align with CWE-252, which addresses "Unchecked Return Value" vulnerabilities that occur when a function's return value is not properly validated or checked for errors. This flaw represents a classic example of how missing validation can create security weaknesses in system-level code. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques, specifically T1068 which covers "Local Privilege Escalation" and potentially T1543 which addresses "Create or Modify System Process" through the ability to gain system-level execution privileges. The lack of user interaction requirement for exploitation makes this vulnerability particularly concerning as it can be leveraged automatically without requiring social engineering or user deception tactics.
Mitigation strategies for this vulnerability should focus on implementing proper return value validation throughout the identity management subsystem, ensuring that all function calls within the ic_startRetrieveEntryValue process properly validate their return codes before proceeding with subsequent operations. System administrators and device manufacturers should prioritize applying security patches that address this specific validation issue, while also implementing monitoring mechanisms to detect anomalous behavior patterns that might indicate exploitation attempts. Additionally, organizations should conduct thorough code reviews of similar functions within the Android kernel to identify and remediate other potential instances of unchecked return values that could present similar security risks.