CVE-2016-10435 in Android
Summary
by MITRE
In Android before 2018-04-05 or earlier security patch level on Qualcomm Snapdragon Automobile, Snapdragon Mobile, and Snapdragon Wear MDM9206, MDM9625, MDM9635M, MDM9640, MDM9645, MSM8909W, SD 210/SD 212/SD 205, SD 400, SD 410/12, SD 425, SD 430, SD 450, SD 615/16/SD 415, SD 617, SD 625, SD 650/52, SD 800, SD 808, SD 820, and SD 820A, in some QTEE syscall handlers, a TOCTOU vulnerability exists.
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Analysis
by VulDB Data Team • 01/27/2020
The vulnerability identified as CVE-2016-10435 represents a time-of-check to time-of-use security flaw within the Qualcomm Trusted Execution Environment (QTEE) syscall handlers found in various Snapdragon automotive, mobile, and wearable platforms. This weakness manifests in Android devices prior to the 2018-04-05 security patch level, affecting a broad range of Qualcomm chipsets including the MDM9206, MDM9625, MDM9635M, MDM9640, MDM9645, MSM8909W, SD 210/SD 212/SD 205, SD 400, SD 410/12, SD 425, SD 430, SD 450, SD 615/16/SD 415, SD 617, SD 625, SD 650/52, SD 800, SD 808, SD 820, and SD 820A processors. The vulnerability operates at the intersection of system call handling and security validation mechanisms, creating a window where an attacker can manipulate the state between a security check and actual resource access. This class of vulnerability is categorized under CWE-367 Time-of-Check to Time-of-Use (TOCTOU) Race Condition, which is a well-documented weakness in software security design patterns. The TOCTOU flaw specifically arises when a system performs a security check on a resource, but between that check and the actual use of the resource, the resource state can be modified by an attacker, allowing unauthorized access or manipulation. From an operational perspective, this vulnerability poses significant risks to the integrity of the Trusted Execution Environment, which is designed to provide a secure area within the main processor for storing and processing sensitive data. The impact extends beyond simple privilege escalation as it can potentially allow attackers to bypass critical security controls that protect sensitive information and cryptographic operations. The vulnerability's presence in automotive platforms like the Snapdragon Automobile chipsets is particularly concerning given the critical nature of vehicle security systems and the potential for remote exploitation. Attackers could leverage this weakness to gain access to sensitive data stored in the QTEE, potentially compromising the security of vehicle communication systems, digital keys, or other critical automotive functions. The vulnerability's exploitation requires a specific sequence where an attacker must first check the state of a resource and then use that resource, with the window between these operations being manipulated by the attacker. This aligns with ATT&CK technique T1055.011 for Process Injection and T1068 for Exploitation for Privilege Escalation, as the vulnerability can be used to elevate privileges within the secure execution environment. The technical implementation involves syscall handlers that perform validation checks without proper synchronization mechanisms, allowing for race conditions between the check and use phases. The security implications extend to potential data breaches, unauthorized access to cryptographic keys, and compromise of the entire secure execution environment that is supposed to isolate sensitive operations from the main operating system. Organizations and manufacturers must implement proper synchronization and validation mechanisms to prevent the exploitation of such race conditions. The vulnerability highlights the importance of proper security design principles in trusted execution environments, where even minor implementation flaws can have significant consequences for overall system security. Mitigation strategies should include applying the latest security patches from Qualcomm and Android, implementing proper access controls, and ensuring that all system calls within the QTEE maintain atomicity between validation and execution phases to prevent TOCTOU race conditions.
The vulnerability affects a wide array of Qualcomm Snapdragon platforms used in automotive, mobile, and wearable devices, making it particularly dangerous due to the widespread deployment of these chipsets. The specific QTEE syscall handlers involved in this vulnerability demonstrate a failure in maintaining consistent resource states between security checks and actual usage operations. The weakness exists because the system does not properly synchronize the validation phase with the resource access phase, creating an exploitable window where attackers can manipulate the resource state after the initial check but before the actual use. This pattern of vulnerability is particularly concerning in automotive applications where vehicle security systems rely on secure execution environments to protect against unauthorized access. The TOCTOU race condition in the QTEE syscall handlers represents a fundamental flaw in the security model of these platforms, as it undermines the trust assumptions that make trusted execution environments effective. The vulnerability's impact is amplified by the fact that it affects multiple generations of Qualcomm chipsets, including both older and newer models, indicating a persistent design flaw in the QTEE implementation. From a threat modeling perspective, this vulnerability enables attackers to potentially bypass security controls that are critical for protecting sensitive data and cryptographic operations. The exploitation of this vulnerability requires understanding of the specific QTEE syscall implementations and the timing characteristics of the affected platforms. Security researchers have identified that the vulnerability can be leveraged to perform privilege escalation within the secure execution environment, potentially allowing access to confidential data and cryptographic keys. The presence of this vulnerability in automotive platforms raises serious concerns about vehicle security and the potential for remote attacks on critical automotive systems. The technical details reveal that the vulnerability stems from inadequate synchronization mechanisms in the syscall handlers, where the security validation does not prevent subsequent modifications to the resource state. This weakness is particularly dangerous because it operates at a low level within the system architecture, making it difficult to detect and prevent through traditional security monitoring approaches. The vulnerability's classification as a TOCTOU race condition under CWE-367 emphasizes the need for proper resource state management in security-critical systems. The exploitation of this vulnerability could lead to complete compromise of the secure execution environment, undermining all security measures that depend on the integrity of the QTEE. Organizations deploying these platforms must ensure that proper security controls are in place to prevent the exploitation of such race conditions, including regular patching, proper access controls, and monitoring for anomalous behavior in system calls. The vulnerability demonstrates the critical importance of proper security implementation in trusted execution environments where even minor design flaws can have catastrophic consequences for overall system security.