CVE-2019-9271 in Android
Summary
by MITRE
In the Android kernel in the mnh driver there is a race condition due to insufficient locking. This could lead to a use-after-free which could lead to escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-9271 resides within the Android kernel's mnh driver, representing a critical race condition flaw that stems from inadequate locking mechanisms. This fundamental design weakness creates a window of opportunity where concurrent access to shared resources can result in unpredictable behavior. The mnh driver, which typically handles multimedia processing functions within Android devices, becomes a potential attack vector when multiple threads attempt to access the same memory locations without proper synchronization. The race condition manifests when the system fails to implement sufficient mutex or semaphore controls to prevent simultaneous access to critical data structures, creating a scenario where one thread may attempt to free memory while another thread is still accessing it. This fundamental flaw aligns with CWE-362, which specifically addresses race conditions in concurrent programming environments where improper synchronization leads to security vulnerabilities. The absence of proper locking protocols means that the kernel cannot guarantee the consistency of shared data structures during concurrent operations, opening the door to exploitation.
The technical exploitation of this vulnerability results in a use-after-free condition that can be leveraged for privilege escalation. When the race condition occurs, it typically involves a scenario where a memory allocation is freed while another process or thread still maintains a reference to it, creating a dangling pointer situation. The attacker can manipulate the timing of concurrent operations to force the system into a state where freed memory is reallocated and accessed in a controlled manner. This allows for the execution of arbitrary code with system-level privileges, effectively bypassing the normal security boundaries that separate user applications from the core operating system. The use-after-free vulnerability specifically enables attackers to corrupt memory contents, potentially leading to code execution at the highest privilege level. This represents a significant departure from typical user-level exploits and directly targets the kernel's memory management subsystem, making it particularly dangerous for mobile device security.
The operational impact of CVE-2019-9271 extends beyond simple privilege escalation, as it fundamentally undermines the security model of Android devices. Since no user interaction is required for exploitation, the vulnerability can be triggered automatically through normal device operations, making it particularly stealthy and dangerous. Attackers can leverage this flaw to gain complete control over affected devices, potentially accessing sensitive user data, installing malicious applications, or even modifying system files. The vulnerability affects devices running Android versions prior to the security patches released in 2019, leaving millions of smartphones and tablets exposed to potential compromise. The lack of user interaction requirement means that this vulnerability can be exploited in the background without the user's knowledge, creating a persistent threat that can be maintained even after device restarts. This characteristic places the vulnerability in the ATT&CK framework under the privilege escalation category, specifically targeting the kernel-level execution environment where attackers can gain system-level access without requiring physical presence or user consent.
Mitigation strategies for CVE-2019-9271 primarily focus on implementing proper locking mechanisms within the mnh driver and ensuring comprehensive kernel updates. Device manufacturers and security researchers recommend immediate deployment of kernel patches that introduce appropriate mutex or spinlock implementations to prevent concurrent access to shared resources. The fix typically involves adding proper synchronization primitives around critical sections of code where the race condition occurs, ensuring that only one thread can access the shared data structure at any given time. Additionally, the implementation of memory safety checks and bounds verification can help detect and prevent exploitation attempts. System administrators should prioritize updating devices to the latest Android security patches, as these updates contain the necessary fixes for the race condition in the mnh driver. The vulnerability also underscores the importance of kernel code review processes, particularly for drivers handling multimedia functions, where concurrent access patterns can create complex synchronization challenges. Regular security audits and static analysis of kernel modules can help identify similar race condition vulnerabilities before they can be exploited in the wild. Organizations should also consider implementing runtime monitoring solutions that can detect anomalous memory access patterns indicative of use-after-free exploitation attempts, providing an additional layer of defense against this and similar vulnerabilities.