CVE-2017-15842 in Android
Summary
by MITRE
Buffer might get used after it gets freed due to unlocking the mutex before freeing the buffer in all Android releases from CAF (Android for MSM, Firefox OS for MSM, QRD Android) using the Linux Kernel.
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Analysis
by VulDB Data Team • 02/18/2020
This vulnerability represents a classic use-after-free condition that occurs in Android kernel implementations across multiple device families including MSM based devices and QRD Android platforms. The flaw manifests when a buffer allocated in kernel space is freed while a mutex lock is still held, creating a window where the buffer could be accessed by concurrent processes or threads before proper deallocation occurs. This specific issue affects Android for MSM, Firefox OS for MSM, and QRD Android releases, indicating a widespread problem within Qualcomm's Android kernel implementations. The vulnerability stems from improper synchronization mechanisms where the mutex unlocking operation occurs before the buffer deallocation, violating fundamental memory management principles.
The technical exploitation of this vulnerability allows attackers to potentially execute arbitrary code or cause system instability through controlled memory access patterns. When the mutex is released before buffer deallocation, concurrent threads may attempt to access the same memory region that has been freed but not yet properly invalidated. This creates a race condition scenario where the attacker can manipulate the timing to either overwrite freed memory with malicious data or cause the system to dereference invalid pointers. The vulnerability is particularly concerning because it operates at the kernel level where privilege escalation is automatic and system-wide impact is possible.
From a cybersecurity perspective, this vulnerability maps directly to CWE-416, which specifically addresses use-after-free conditions in memory management. The operational impact extends beyond simple denial of service to potential privilege escalation and system compromise. Attackers could leverage this condition to execute malicious code with kernel privileges, effectively bypassing standard security boundaries. The ATT&CK framework would categorize this under privilege escalation techniques, specifically targeting kernel-level vulnerabilities that allow adversaries to gain elevated system access. The widespread nature of affected platforms means that numerous devices across different manufacturers could be vulnerable, particularly those utilizing Qualcomm's MSM chipsets.
Mitigation strategies should focus on proper synchronization mechanisms and ensuring that mutex locks are released only after buffer deallocation is complete. Kernel patches should enforce strict ordering of operations to prevent race conditions, and developers should implement proper memory management protocols that maintain buffer validity until all potential accessors have completed their operations. System administrators should prioritize updating affected Android versions and ensure that kernel patches addressing this specific race condition are deployed across all vulnerable platforms. Additionally, runtime monitoring and memory protection mechanisms can help detect and prevent exploitation attempts, though the fundamental fix requires addressing the underlying synchronization logic in kernel implementations.