CVE-2018-21040 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with O(8.x) and P(9.0) (Exynos 9810 chipsets) software. There is a race condition with a resultant use-after-free in the g2d driver. The Samsung ID is SVE-2018-12959 (December 2018).
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Analysis
by VulDB Data Team • 10/07/2020
The vulnerability CVE-2018-21040 represents a critical race condition flaw within the graphics 2D (g2d) driver component of Samsung's mobile devices running Android 8.x and 9.0 operating systems. This issue specifically affects devices equipped with Exynos 9810 chipsets, which were widely deployed in Samsung Galaxy S8, S8+, and Note 8 devices. The vulnerability stems from improper synchronization mechanisms within the kernel-level graphics driver, creating an environment where concurrent access patterns can lead to memory corruption. The race condition manifests when multiple threads attempt to access shared resources within the g2d driver without proper mutual exclusion controls, resulting in unpredictable behavior that can be exploited by malicious actors.
The technical flaw constitutes a use-after-free vulnerability that emerges from the race condition in the g2d driver implementation. When the driver processes graphics operations concurrently, it fails to properly protect critical sections of code that manage memory allocation and deallocation. This allows an attacker to manipulate the timing of operations such that a memory region is freed while another thread still references it, creating a use-after-free condition. The flaw is particularly dangerous because it occurs in kernel space, where exploitation can lead to privilege escalation and full system compromise. The vulnerability affects the graphics processing unit's memory management subsystem, specifically within the Exynos 9810's hardware abstraction layer that interfaces with Android's graphics framework.
The operational impact of this vulnerability is severe and multifaceted across the Samsung device ecosystem. Attackers can exploit this condition to execute arbitrary code with kernel-level privileges, effectively bypassing Android's security model and gaining complete control over affected devices. The use-after-free condition can be leveraged to escalate privileges from a regular application to system-level access, enabling unauthorized modifications to system files, data exfiltration, and persistent backdoor installation. Additionally, the vulnerability affects the device's graphics processing capabilities, potentially causing system instability or denial of service conditions. Given that these devices were widely deployed and many users continued to use them without regular security updates, the exploitation potential was significant.
Mitigation strategies for CVE-2018-21040 require both immediate patching and operational security measures to protect affected Samsung devices. Samsung released security patches addressing this vulnerability through their regular security update cycle, but many users failed to install these updates due to various deployment and awareness issues. System administrators and security teams should prioritize updating all affected devices to the latest security patches, particularly those running Android 8.x and 9.0 versions on Exynos 9810 chipsets. Device manufacturers should implement proper kernel memory management controls and race condition prevention mechanisms, including enhanced mutex locking and proper synchronization primitives. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and relates to ATT&CK technique T1068, involving exploit for privilege escalation. Organizations should also consider implementing network-based monitoring to detect exploitation attempts and maintain robust backup and recovery procedures for affected systems.