CVE-2018-21085

Vulnerability

A race condition exists in the vnswap_deinit_backing_storage function on Samsung mobile devices running Android versions L (5.x), M (6.0), and N (7.x). The vulnerability leads to a use-after-free condition due to improper synchronization when deinitializing swap backing storage. Affected software versions are explicitly those with L(5.x), M(6.0), and N(7.x) as referenced by Samsung's security update [1].

Exploitation

An attacker requires local access to the device to trigger the race condition in the vnswap_deinit_backing_storage code path. The exploitation sequence involves exploiting the timing window between memory allocation and deallocation, leading to a use-after-free. No user interaction beyond normal system usage is needed, but the attacker must be able to execute code with sufficient privileges to invoke the vulnerable function.

Impact

Successful exploitation results in memory corruption, potentially allowing an attacker to execute arbitrary code with kernel privileges. This can lead to full compromise of the device, including unauthorized access to sensitive data, modification of system files, and persistent control over the device. The impact is high due to the kernel-level access gained.

Mitigation

Samsung released a security update as part of its monthly Security Maintenance Release (SMR) process. The fix was included in the February 2018 update, as indicated by the Samsung ID SVE-2017-11176 [1]. Users should ensure their devices are updated to the latest firmware version to mitigate this vulnerability. No workarounds are provided for unpatched devices.