CVE-2023-21116 in Android
Summary
by MITRE • 05/16/2023
In verifyReplacingVersionCode of InstallPackageHelper.java, there is a possible way to downgrade system apps below system image version due to a logic error in the code. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11 Android-12 Android-12L Android-13Android ID: A-256202273
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Analysis
by VulDB Data Team • 09/13/2025
The vulnerability identified as CVE-2023-21116 resides within the Android system's package installation mechanism, specifically in the verifyReplacingVersionCode method of the InstallPackageHelper.java component. This flaw represents a critical security weakness that allows malicious actors to potentially downgrade system applications to versions older than those present in the system image. The vulnerability affects multiple Android versions including Android 11, 12, 12L, and 13, indicating a widespread impact across the Android ecosystem. The logical error in the verification process creates an exploitable condition that undermines the integrity of the system's package management system.
The technical implementation of this vulnerability stems from improper validation logic within the package installation framework that fails to adequately verify version compatibility during system app updates. When a system application is being replaced or updated, the system should enforce strict version controls to prevent downgrade scenarios that could introduce known security vulnerabilities or unstable code versions. However, the flawed implementation in InstallPackageHelper.java allows for bypassing these critical checks, enabling an attacker to install older versions of system applications that may contain unpatched security flaws or backdoors. This logical error creates a pathway for privilege escalation by allowing modification of system components that should remain at or above the baseline system image version.
The operational impact of this vulnerability is severe and directly relates to local privilege escalation capabilities. An attacker with local system access can exploit this flaw to downgrade system applications to versions that may contain known vulnerabilities or malicious code. Since the system image contains the baseline security posture and stability requirements, allowing downgrades below these versions compromises the entire system integrity. The vulnerability requires system execution privileges for exploitation, but once achieved, it can provide attackers with the ability to manipulate core system components. This creates a significant risk for device security, as downgraded system applications may lack critical security patches or may have been specifically modified to include malicious functionality. The attack vector does not require user interaction, making it particularly dangerous as it can be exploited automatically without any human intervention.
The vulnerability aligns with CWE-284 Access Control Issues and represents a failure in privilege management within the Android system. It also maps to ATT&CK technique T1068 Privilege Escalation through the exploitation of system component integrity violations. The flaw essentially creates a backdoor mechanism that allows unauthorized modification of system applications, potentially enabling attackers to establish persistent access or execute malicious code with system-level privileges. Organizations should immediately implement mitigations including applying the latest security patches, monitoring system application installations for unauthorized modifications, and implementing strict access controls for system-level operations. The vulnerability demonstrates the critical importance of maintaining proper version control and integrity checks within system package managers, as these mechanisms form the foundation of Android's security architecture. Security teams should also consider implementing additional monitoring for system application downgrade attempts and establish incident response procedures for detecting and mitigating such exploitation attempts.