CVE-2021-0691 in Android
Summary
by MITRE • 10/06/2021
In the SELinux policy configured in system_app.te, there is a possible way for system_app to gain code execution in other processes due to an overly-permissive SELinux policy. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11Android ID: A-188554048
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Analysis
by VulDB Data Team • 10/09/2021
The vulnerability described in CVE-2021-0691 represents a critical security flaw within Android's Security-Enhanced Linux (SELinux) implementation that affects Android 11 systems. This issue resides in the system_app.te policy file, which defines the security context and permissions for system applications within the Android framework. The flaw stems from an overly permissive SELinux policy configuration that inadvertently grants system_app processes elevated privileges beyond their intended scope, creating a potential pathway for privilege escalation attacks.
The technical nature of this vulnerability involves improper access control mechanisms within the SELinux policy enforcement system. Specifically, the system_app.te policy file contains configuration that allows system_app processes to execute code within other processes that should normally be isolated from such operations. This misconfiguration creates a security boundary violation where a compromised system_app could potentially inject malicious code or manipulate the execution flow of other processes. The vulnerability operates at the kernel level within the SELinux framework, leveraging the policy enforcement mechanisms to bypass normal security restrictions that should prevent such cross-process code execution.
From an operational impact perspective, this vulnerability enables local privilege escalation attacks where a malicious application with system_app privileges could potentially execute arbitrary code in the context of other processes with higher privileges. The attack requires only system execution privileges to be successful, meaning that an attacker who has already compromised a system_app process could leverage this flaw to gain broader system access. This represents a significant threat to Android's security model since it undermines the fundamental principle of process isolation that SELinux is designed to enforce. The vulnerability affects the entire Android 11 ecosystem and could potentially compromise device integrity, user data confidentiality, and overall system security posture.
The mitigation strategies for CVE-2021-0691 should focus on tightening the SELinux policy restrictions within the system_app.te file to eliminate the overly permissive configurations. Android security updates typically address such issues by revising the policy definitions to enforce stricter access controls and process boundaries. Organizations should ensure timely deployment of security patches and updates that correct the policy configuration to prevent system_app processes from gaining unauthorized code execution capabilities in other processes. Additionally, security monitoring should be enhanced to detect anomalous behavior patterns that might indicate exploitation attempts, while adherence to the principle of least privilege should be maintained across all system components. This vulnerability aligns with CWE-276, which addresses improper privilege management, and represents a significant concern for the ATT&CK framework's privilege escalation techniques, specifically targeting the use of system-level access to gain broader system control.