CVE-2014-9937 in Android
Summary
by MITRE
In TrustZone a buffer overflow vulnerability can potentially occur in a DRM routine in all Android releases from CAF using the Linux kernel.
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Analysis
by VulDB Data Team • 12/24/2020
The vulnerability identified as CVE-2014-9937 represents a critical buffer overflow condition within the TrustZone security framework of Android devices. This flaw exists in the Digital Rights Management (DRM) processing routines that are part of the Android Common Audio Framework (CAF) implementation. The vulnerability manifests specifically within the Linux kernel components that handle DRM operations, making it particularly dangerous as it operates at a low-level system interface where privilege escalation opportunities are abundant.
The technical implementation of this buffer overflow occurs when the TrustZone subsystem processes DRM content through kernel modules that lack proper bounds checking mechanisms. The vulnerability arises from insufficient input validation in the DRM handling code path, allowing maliciously crafted data to overwrite adjacent memory regions within the kernel space. This flaw is particularly concerning because TrustZone represents a secure execution environment that is designed to isolate sensitive operations from the main operating system, yet the buffer overflow allows attackers to potentially breach this isolation boundary.
The operational impact of CVE-2014-9937 extends beyond typical buffer overflow consequences as it affects all Android releases that utilize the CAF framework with Linux kernel implementations. Attackers can exploit this vulnerability to execute arbitrary code within the kernel context, potentially gaining full system control. The vulnerability's presence in the TrustZone environment means that even if the main operating system is compromised, attackers could leverage this flaw to access secure elements that should remain protected. This represents a significant weakening of the security model that TrustZone is designed to provide, as outlined in the CWE-121 category for buffer overflow conditions.
From an adversary perspective, this vulnerability aligns with ATT&CK technique T1068 which involves local privilege escalation through kernel exploits. The attack surface is particularly broad given that the vulnerability affects multiple Android versions and device manufacturers that implement CAF. The exploitability of this vulnerability is enhanced by the fact that it operates at the kernel level, eliminating the need for complex attack chains that would typically be required to reach such privileged execution contexts. This makes the vulnerability particularly attractive to threat actors seeking persistent access to mobile devices.
Mitigation strategies for CVE-2014-9937 should focus on immediate patching of affected kernel versions and implementation of kernel memory protection mechanisms such as stack canaries and address space layout randomization. Device manufacturers should consider implementing runtime integrity checks for DRM processing routines and strengthen input validation procedures in kernel modules. The vulnerability also highlights the importance of secure coding practices and adherence to security guidelines for kernel development, particularly when implementing trusted execution environments like TrustZone. Organizations should also implement monitoring for anomalous kernel behavior that could indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of secure kernel development practices and the need for continuous security assessment of trusted execution environments that are fundamental to modern mobile security architectures.