CVE-2016-3893 in Android
Summary
by MITRE
The wcdcal_hwdep_ioctl_shared function in sound/soc/codecs/wcdcal-hwdep.c in the Qualcomm sound codec in Android before 2016-09-05 on Nexus 6P devices does not properly copy firmware data, which allows attackers to obtain sensitive information via a crafted application, aka Android internal bug 29512527 and Qualcomm internal bug CR856400.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-3893 represents a critical information disclosure flaw within the Qualcomm sound codec implementation on Android devices, specifically affecting Nexus 6P models prior to the 2016-09-05 security update. This issue resides in the wcdcal_hwdep_ioctl_shared function located within the sound/soc/codecs/wcdcal-hwdep.c file, which serves as a hardware-dependent interface for the WCD (WCD9340) codec driver. The flaw stems from improper handling of firmware data copying operations, creating a pathway for malicious applications to extract sensitive information from kernel memory spaces. The vulnerability is particularly concerning as it affects the core audio subsystem that manages critical audio hardware components including microphone inputs, speaker outputs, and audio processing pipelines. This weakness enables attackers to leverage crafted applications to perform unauthorized memory reads, potentially accessing confidential data that should remain protected within the kernel's memory boundaries.
The technical implementation of this vulnerability demonstrates a classic buffer over-read condition where the function fails to properly validate or copy firmware data structures, leading to information leakage from kernel memory regions. The flaw occurs during ioctl (input/output control) operations that are typically used for device-specific commands and configuration, specifically within the hardware-dependent interface layer that bridges user-space applications with kernel-space audio hardware drivers. According to CWE classification, this vulnerability maps to CWE-125: Out-of-bounds Read, which describes an instance where a program reads data past the end, or before the beginning, of the intended buffer. The operational impact is significant as it allows for privilege escalation and information disclosure attacks that can reveal sensitive data such as cryptographic keys, system memory contents, or other confidential information that should remain isolated from user-space applications. The vulnerability affects the Android security model by undermining the kernel's memory protection mechanisms and potentially exposing the underlying hardware configuration data that could be used for further exploitation.
From an operational perspective, this vulnerability provides attackers with a means to extract sensitive information from the kernel memory space through legitimate ioctl interface calls, effectively bypassing normal security boundaries. The attack vector requires a malicious application with appropriate permissions to execute the crafted ioctl commands that trigger the improper data copying mechanism. This flaw aligns with ATT&CK technique T1059.003 for Command and Scripting Interpreter: Windows Command Shell, as it enables execution of malicious commands through kernel interfaces, though adapted for Android environments. The vulnerability's impact extends beyond simple information disclosure to potentially enable more sophisticated attacks including privilege escalation, as access to kernel memory can reveal system configuration details and memory layouts that aid in developing further exploits. The affected Nexus 6P devices represent a significant portion of Android users at the time, making this vulnerability particularly dangerous as it could be exploited across a wide user base without requiring physical access or specialized hardware. The vulnerability also demonstrates a failure in proper input validation and memory management practices within the kernel driver code, highlighting the importance of robust security controls in system-level software components.
The recommended mitigations for this vulnerability include applying the official Android security patches released on or before 2016-09-05, which contain proper bounds checking and memory copy operations within the wcdcal_hwdep_ioctl_shared function. System administrators should ensure all devices are updated to the latest security patches, particularly focusing on the Qualcomm audio codec drivers and the Android kernel components. Additional protective measures include implementing application sandboxing and restricting access to hardware-dependent interfaces, though these measures are secondary to the primary fix. The vulnerability serves as a reminder of the critical importance of secure coding practices in kernel-level drivers, particularly regarding memory management and input validation. Organizations should conduct regular security assessments of their Android device fleets and implement proper patch management procedures to ensure timely deployment of security fixes. The flaw also underscores the need for comprehensive testing of kernel interfaces and the importance of following secure coding guidelines such as those outlined in the CERT Secure Coding Standards for embedded systems and mobile platforms.