CVE-2009-1754 in Android
Summary
by MITRE
The PackageManagerService class in services/java/com/android/server/PackageManagerService.java in Android 1.5 through 1.5 CRB42 does not properly check developer certificates during processing of sharedUserId requests at an application s installation time, which allows remote user-assisted attackers to access application data by creating a package that specifies a shared user ID with an arbitrary application.
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Analysis
by VulDB Data Team • 08/11/2021
The vulnerability described in CVE-2009-1754 represents a critical security flaw in the Android operating system's package management architecture that existed from version 1.5 through the CRB42 release. This weakness resides within the PackageManagerService component which serves as the central authority for managing application installations and permissions on Android devices. The flaw specifically manifests during the installation process when the system processes sharedUserId requests, which are mechanisms that allow multiple applications to share the same Linux user ID and thus access each other's data and resources. The vulnerability stems from insufficient validation of developer certificates that should normally verify the authenticity and authorization of applications attempting to use shared user IDs. Attackers can exploit this by crafting malicious packages that specify shared user IDs with existing applications, effectively bypassing the normal security checks that should prevent unauthorized access to application data.
The technical nature of this vulnerability aligns with CWE-284, which describes improper access control mechanisms, and represents a direct failure in the Android security model's permission enforcement system. When an application attempts to install with a shared user ID, the PackageManagerService should validate that the requesting application's certificate matches the certificate of the application already registered with that shared user ID. However, the implementation in affected Android versions fails to perform this critical certificate verification step, allowing malicious actors to create applications that can masquerade as legitimate applications and gain unauthorized access to their data. This flaw operates under the principle that applications sharing the same user ID should be from the same developer or at least authorized to access each other's resources, but the missing certificate check removes this crucial verification layer.
The operational impact of CVE-2009-1754 extends beyond simple data access, as it enables a sophisticated attack vector that can compromise the entire application sandbox model that Android relies upon for security isolation. An attacker can exploit this vulnerability to create a malicious application that shares the same user ID as a legitimate application, thereby gaining access to that application's private data, databases, and shared preferences. This represents a significant escalation from typical Android permissions, as it essentially allows one application to completely subvert another's security boundaries. The vulnerability is particularly dangerous because it requires no special privileges or device root access, making it exploitable through standard application installation mechanisms. From an attacker's perspective, this flaw aligns with ATT&CK technique T1068, which involves exploiting legitimate credentials or privileges, and T1546, which covers privilege escalation through application installation.
The exploitation of this vulnerability demonstrates a fundamental breakdown in Android's security architecture that allowed for unauthorized data access and potential privilege escalation. When an application with a matching shared user ID is installed, the system should verify that the certificate used to sign the new application matches the certificate of the existing application sharing that user ID. This certificate verification ensures that only applications from the same developer can share resources, maintaining the security isolation that prevents one application from accessing another's data without proper authorization. The absence of this check means that any malicious application can potentially gain access to applications that share user IDs, effectively allowing data theft, privacy violations, and potential system compromise through unauthorized access to sensitive application resources and data stores. Organizations and users were particularly vulnerable because this attack could be executed through standard app installation processes, making detection difficult and exploitation straightforward.
Mitigation strategies for CVE-2009-1754 required immediate system updates and architectural improvements to the package management system. The primary fix involved implementing proper certificate validation during shared user ID processing, ensuring that applications attempting to use shared user IDs must present valid certificates that match those of existing applications sharing the same user ID. This solution aligns with security best practices outlined in the OWASP Mobile Security Project and follows the principle of least privilege enforcement. Additionally, Android developers and security teams needed to implement proper application signing practices and certificate management to prevent unauthorized certificate usage. The vulnerability highlighted the importance of comprehensive security testing during the development lifecycle and demonstrated the critical need for proper access control mechanisms in mobile operating systems. System administrators and device manufacturers should have implemented immediate security patches and monitored for suspicious application installations that might attempt to exploit this vulnerability, particularly focusing on applications that requested shared user IDs or attempted to access other applications' data through these mechanisms.