CVE-2021-0342 in Android
Summary
by MITRE • 01/12/2021
In tun_get_user of tun.c, there is possible memory corruption due to a use after free. This could lead to local escalation of privilege with System execution privileges required. User interaction is not required for exploitation. Product: Android; Versions: Android kernel; Android ID: A-146554327.
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Analysis
by VulDB Data Team • 08/08/2025
The vulnerability identified as CVE-2021-0342 resides within the Android kernel's TUN (Tunnel) network driver implementation, specifically in the tun_get_user function located in the tun.c source file. This represents a critical memory safety issue that could potentially be exploited to achieve local privilege escalation. The flaw manifests as a use-after-free condition, where memory that has been freed is subsequently accessed, creating opportunities for arbitrary code execution. The vulnerability is particularly concerning because it requires only system execution privileges for exploitation, meaning an attacker with minimal access could leverage this weakness to gain elevated privileges. The Android ID A-146554327 indicates this issue was tracked within Google's internal Android security framework, highlighting its significance in the mobile operating system ecosystem.
The technical root cause of this vulnerability stems from improper memory management within the TUN driver's user space interface handling. When the tun_get_user function processes data transfers between kernel and user space, it appears to free memory resources without ensuring proper synchronization or validation before subsequent access attempts. This use-after-free scenario creates a predictable memory layout that could be manipulated by an attacker to overwrite critical kernel data structures or execute arbitrary code. The vulnerability operates at the kernel level, making it particularly dangerous as it can bypass traditional user-space security mechanisms. According to CWE classification, this maps to CWE-416 Use After Free, which is categorized under memory safety vulnerabilities and represents one of the most prevalent classes of bugs leading to privilege escalation attacks. The ATT&CK framework would classify this under privilege escalation techniques, specifically targeting kernel-level exploits that leverage memory corruption vulnerabilities.
The operational impact of CVE-2021-0342 extends beyond simple local privilege escalation, as it fundamentally undermines the security model of the Android kernel. An attacker could potentially exploit this vulnerability to execute code with kernel-level privileges, enabling complete system compromise. The lack of user interaction requirement makes this vulnerability particularly dangerous for mobile devices, as it could be exploited through automated means without requiring physical access or user deception. The memory corruption could potentially lead to system crashes, data corruption, or more sinisterly, persistent backdoor installation. This vulnerability affects all Android kernel versions that implement the TUN network driver, making it a widespread concern across the mobile ecosystem. The exploitation process would likely involve carefully crafted network traffic or TUN interface operations that trigger the specific code path containing the use-after-free condition, allowing an attacker to manipulate memory contents to achieve their desired privileges.
Mitigation strategies for CVE-2021-0342 should focus on both immediate patching and operational security measures. Android device manufacturers and security teams should prioritize applying the relevant kernel patches that address the memory management issues in the TUN driver implementation. The fix typically involves ensuring proper synchronization mechanisms are in place and that memory resources are not accessed after being freed. Organizations should also implement monitoring for unusual network traffic patterns that might indicate exploitation attempts, particularly around TUN interface usage. Network segmentation and access controls can help limit the potential impact if exploitation occurs. Additionally, regular security audits of kernel modules and network drivers should be conducted to identify similar memory safety issues. The vulnerability demonstrates the critical importance of thorough code review processes for kernel-level components, particularly those handling user-space interfaces, and underscores the need for comprehensive fuzzing and static analysis tools in the security testing pipeline. Security teams should also consider implementing kernel memory protection mechanisms such as stack canaries and memory layout randomization to further reduce exploitability.