CVE-2020-0485 in Android
Summary
by MITRE • 12/15/2020
In areFunctionsSupported of UsbBackend.java, there is a possible access to tethering from a guest account due to a missing permission check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11Android ID: A-166125765
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Analysis
by VulDB Data Team • 12/18/2020
The vulnerability identified as CVE-2020-0485 resides within the USB backend functionality of Android operating systems, specifically in the areFunctionsSupported method of the UsbBackend.java file. This flaw represents a critical security oversight that allows unauthorized access to tethering capabilities from guest user accounts, effectively bypassing intended permission boundaries. The vulnerability manifests through a missing permission check mechanism that should normally restrict access to tethering functions to privileged user accounts only. The absence of this validation creates a path for privilege escalation that requires no additional execution privileges beyond the initial guest account access, making it particularly concerning from a security perspective. This issue affects Android 11 and potentially earlier versions where the USB backend implementation remains unchanged.
The technical nature of this vulnerability aligns with CWE-284, which addresses improper access control mechanisms in software systems. The flaw operates at the system-level permission enforcement layer where guest accounts should be restricted from accessing certain network functionality. The UsbBackend.java component serves as a bridge between USB hardware interfaces and system network management functions, and the missing permission verification creates an exploitable gap in the Android security model. This particular implementation flaw demonstrates poor adherence to the principle of least privilege, where guest accounts should have minimal system access rights but can still manipulate network tethering settings through this bypass.
The operational impact of CVE-2020-0485 extends beyond simple privilege escalation to potentially enable broader network-based attacks. An attacker with guest account access could leverage this vulnerability to establish unauthorized network connections, potentially accessing sensitive data or creating backdoor communication channels. The lack of user interaction requirements for exploitation makes this vulnerability particularly dangerous as it can be triggered automatically without requiring any user engagement or specific actions. This characteristic places the vulnerability in the ATT&CK framework under privilege escalation techniques where adversaries can move laterally within a system without additional attack vectors. The vulnerability could enable attackers to gain persistent access to network resources that should normally be restricted to administrative accounts.
Mitigation strategies for this vulnerability should focus on implementing proper permission checks within the USB backend component and ensuring that all network-related functions properly validate user privileges before execution. Android security patches should enforce strict access controls for tethering functions, requiring explicit administrative privileges or specific user permissions before allowing access to these network management capabilities. System administrators should ensure that all Android devices are updated with the latest security patches that address this specific vulnerability. Organizations should also consider implementing additional monitoring for unauthorized network tethering activities as a defensive measure. The fix should involve adding comprehensive permission verification within the areFunctionsSupported method to ensure that only authorized user accounts can access tethering functionality, thereby preventing guest accounts from exploiting this privilege escalation path.