CVE-2020-0429 in Android
Summary
by MITRE
In l2tp_session_delete and related functions of l2tp_core.c, there is possible memory corruption due to a use after free. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-152735806
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Analysis
by VulDB Data Team • 09/18/2020
The vulnerability identified as CVE-2020-0429 represents a critical memory corruption issue within the Linux kernel's Layer Two Tunneling Protocol implementation, specifically affecting the l2tp_session_delete function and associated routines in l2tp_core.c. This flaw constitutes a use after free vulnerability that occurs when memory allocated to an L2TP session is freed but subsequently accessed by other kernel functions, creating a potential pathway for malicious exploitation. The vulnerability exists within the Android kernel ecosystem and was assigned Android ID A-152735806, highlighting its significance in mobile device security. The nature of this vulnerability places it squarely within CWE-416, which categorizes use after free conditions as a fundamental memory safety issue that can lead to arbitrary code execution.
The technical implementation of this vulnerability stems from improper memory management within the L2TP core subsystem where session deletion operations do not adequately prevent subsequent references to freed memory structures. When l2tp_session_delete is invoked, it frees kernel memory allocated to L2TP session data structures, but the underlying code fails to properly invalidate all references or pointers to these freed resources. This allows for potential reuse of the freed memory block by other kernel functions, creating opportunities for attackers to manipulate the memory layout and execute malicious code with kernel privileges. The vulnerability requires system execution privileges for exploitation, meaning an attacker must already have access to the device to leverage this flaw, though the ultimate impact includes local privilege escalation to root level access.
The operational impact of CVE-2020-0429 extends beyond simple memory corruption, as it provides a pathway for local privilege escalation that could enable attackers to gain complete system control. This vulnerability affects Android devices running kernel versions that include the vulnerable l2tp_core.c implementation, potentially compromising millions of mobile devices through unauthorized access to kernel memory spaces. The exploitation scenario typically involves an attacker with local access to an Android device who can trigger the L2TP session deletion process, leading to a state where freed memory can be manipulated to execute arbitrary code with system-level privileges. This type of vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and represents a common attack vector for gaining elevated system access in mobile environments.
Mitigation strategies for CVE-2020-0429 should focus on immediate kernel updates and patches provided by Android security teams, as well as implementing robust memory management practices within L2TP implementations. System administrators and device manufacturers should prioritize applying the latest security patches that address the use after free condition in l2tp_core.c, ensuring that all memory references are properly invalidated upon session deletion. Additionally, implementing kernel memory protection mechanisms such as stack canaries, address space layout randomization, and kernel address space layout randomization can help prevent exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper memory management in kernel code, particularly in network protocol implementations where session management and resource cleanup are essential for system stability and security. Organizations should also consider implementing monitoring solutions to detect anomalous kernel memory access patterns that could indicate exploitation attempts.