CVE-2017-15849 in Android
Summary
by MITRE
In Android for MSM, Firefox OS for MSM, QRD Android, with all Android releases from CAF using the Linux kernel, a LayerStack can be destroyed in between Validate and Commit by the application resulting in a Use After Free condition.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 12/20/2019
This vulnerability exists within the Android operating system framework and specifically affects devices utilizing the Linux kernel through the Code Aurora Forum CAF implementations. The flaw manifests in the graphics rendering pipeline where a LayerStack object can be prematurely destroyed between the validation phase and commit phase of rendering operations. This creates a classic use-after-free condition that allows malicious applications to exploit the memory management inconsistency. The vulnerability impacts multiple Android variants including MSM (Mobile Services Module) implementations and Firefox OS for MSM platforms, indicating a widespread issue across mobile operating systems that rely on similar graphics frameworks.
The technical exploitation occurs when an application manipulates the graphics layer stack during the rendering process, specifically targeting the timing window between Validate and Commit operations. During this window, if the application destroys a LayerStack object that is still referenced by the graphics subsystem, subsequent access to that freed memory location results in undefined behavior. The vulnerability leverages the inherent race condition in the graphics rendering pipeline where memory deallocation occurs before all references are properly handled. This type of flaw falls under CWE-416, representing Use After Free conditions, and can be categorized under ATT&CK technique T1068 for local privilege escalation through memory corruption.
The operational impact of this vulnerability extends beyond simple application crashes, as it provides a potential pathway for arbitrary code execution. An attacker could craft malicious applications that specifically target this timing window to overwrite memory contents, potentially leading to privilege escalation or complete system compromise. The vulnerability is particularly concerning because it affects the core graphics rendering framework, which is heavily utilized across all mobile applications, making exploitation relatively straightforward. The affected platforms include various Android releases from CAF and QRD Android implementations, indicating that this is not a temporary issue but a systemic problem within the graphics stack architecture. This vulnerability demonstrates a critical flaw in the memory management protocols within the Android graphics subsystem, where proper reference counting or object lifecycle management has been compromised, allowing attackers to manipulate memory state during critical rendering operations.
Mitigation strategies should focus on implementing proper synchronization mechanisms between the Validate and Commit phases of the graphics rendering pipeline. System-level patches should enforce stricter object lifecycle management and ensure that LayerStack objects remain valid during the entire rendering process. Developers should implement additional checks to prevent premature deallocation and establish proper memory barriers during critical rendering operations. The Android security team should also consider implementing runtime protections such as heap randomization and stack canaries to make exploitation more difficult. Organizations should prioritize updating their devices to patched versions and monitor for any suspicious application behavior that might indicate exploitation attempts. Additionally, security researchers should conduct comprehensive testing of graphics rendering components to identify similar timing window vulnerabilities that might exist in other parts of the system architecture.