CVE-2021-0655 in MT6873
Summary
by MITRE • 11/18/2021
In mdlactl driver, there is a possible memory corruption due to an incorrect bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS05673424; Issue ID: ALPS05673424.
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Analysis
by VulDB Data Team • 11/22/2021
The vulnerability identified as CVE-2021-0655 affects the mdlactl driver component within Android systems, representing a critical memory corruption flaw that stems from an improper bounds check implementation. This issue resides in the kernel-level driver responsible for managing certain hardware functionalities, specifically related to the mdla (Media Data Layer Accelerator) subsystem. The flaw manifests when the driver processes input data without adequate validation of array boundaries, creating opportunities for memory corruption that can be exploited to gain elevated privileges. The vulnerability is particularly concerning because it does not require user interaction for exploitation, making it a silent threat that can be leveraged by malicious actors with local access to the system. The affected driver operates at a low level within the operating system, making the potential impact of exploitation significant given the privileged execution context required for successful privilege escalation. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which specifically addresses issues where array indices are not properly validated before use. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1068 which involves the use of local privilege escalation techniques to gain system-level access.
The technical implementation of this vulnerability occurs within the mdlactl driver's handling of data structures that are processed through kernel space operations. When the driver receives input data from user space applications or system processes, it fails to properly validate the size or boundaries of the data being processed, particularly in scenarios involving arrays or buffers that are dynamically allocated or resized. This inadequate bounds checking allows for potential buffer overflows or underflows that can overwrite adjacent memory locations, potentially corrupting critical data structures or executable code. The memory corruption typically occurs when the driver attempts to write data beyond the allocated buffer boundaries, which can result in unpredictable behavior including system crashes or more dangerously, the ability to execute arbitrary code with system privileges. The specific nature of the bounds check failure suggests that the driver may be using incorrect calculations for buffer sizes or failing to validate input parameters against expected ranges before processing.
The operational impact of CVE-2021-0655 extends beyond simple system instability to represent a significant security risk for devices running affected Android versions. Successful exploitation of this vulnerability can result in local privilege escalation, allowing an attacker with minimal system access to elevate their privileges to the system level, which provides complete control over the device. This capability enables attackers to bypass normal security restrictions, access sensitive data, modify system files, install malicious software, or establish persistent backdoors. The lack of user interaction requirement makes this vulnerability particularly dangerous as it can be exploited automatically without any user awareness or consent. The patch ID ALPS05673424 indicates that this vulnerability was addressed through a specific firmware or kernel update targeting the mdla driver component. Devices running vulnerable versions are at risk of being compromised by attackers who can leverage this flaw to gain unauthorized access to system resources, potentially leading to data breaches, device takeover, or use in larger attack campaigns against connected networks.
Mitigation strategies for CVE-2021-0655 should prioritize immediate deployment of the vendor-provided patch identified by ALPS05673424, which specifically addresses the bounds check implementation within the mdlactl driver. Organizations and users should ensure that all affected devices receive the necessary firmware or kernel updates as soon as possible, particularly those running Android versions prior to the patched release. System administrators should conduct comprehensive vulnerability assessments to identify all devices that may be running vulnerable versions of the mdla driver, especially in enterprise environments where multiple devices may be affected. Additional defensive measures include implementing monitoring solutions that can detect unusual kernel-level activities or memory access patterns that might indicate exploitation attempts. The vulnerability's nature suggests that runtime protections such as stack canaries, address space layout randomization, or kernel address space layout randomization could provide additional layers of defense, though these are secondary to the primary patching requirement. Security teams should also consider implementing network-based intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability. Given the low interaction requirement and high privilege escalation potential, organizations should treat this vulnerability as a critical priority and implement immediate remediation measures to protect their systems from potential compromise.