CVE-2021-39732 in Android
Summary
by MITRE • 03/16/2022
In copy_io_entries of lwis_ioctl.c, there is a possible out of bounds write due to an integer overflow. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-205992503References: N/A
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Analysis
by VulDB Data Team • 03/19/2022
The vulnerability identified as CVE-2021-39732 resides within the Android kernel's lwis_ioctl.c component where the copy_io_entries function exhibits a critical out of bounds write condition stemming from integer overflow. This flaw represents a significant security weakness that allows for local privilege escalation without requiring any additional execution privileges or user interaction for exploitation. The vulnerability specifically manifests in the handling of ioctl (input/output control) operations within the Linux kernel's lwis driver, which is responsible for managing certain hardware interface operations. The integer overflow occurs when processing input parameters that control the copying of I/O entries, creating a scenario where an attacker can manipulate the size calculations to exceed the bounds of allocated memory buffers.
The technical implementation of this vulnerability involves the manipulation of integer variables that control memory allocation and data copying operations. When the copy_io_entries function processes user-supplied parameters, it fails to properly validate or sanitize the size values, allowing an integer overflow to occur during arithmetic operations. This overflow results in a situation where the calculated buffer size becomes smaller than the actual data being copied, leading to memory corruption that can be exploited to overwrite adjacent memory locations. The flaw directly maps to CWE-190, Integer Overflow or Wraparound, which is classified as a fundamental weakness in data handling and validation mechanisms. The vulnerability's exploitation path follows the ATT&CK technique T1068, Exploitation for Privilege Escalation, where local attackers can leverage kernel-level flaws to gain elevated privileges.
The operational impact of this vulnerability is severe as it provides a direct pathway for local attackers to escalate their privileges from regular user level to kernel level execution. This means that any user with access to the system can potentially exploit this vulnerability to gain root access, making it particularly dangerous in multi-user environments or when the device is compromised through other attack vectors. The lack of requirement for user interaction makes the vulnerability especially concerning as it can be exploited automatically without any human intervention. The Android kernel's lwis driver is typically involved in hardware abstraction layer operations, making the exploitation potential widespread across various Android devices that utilize this kernel component. The vulnerability affects Android kernel versions and is tracked under Android ID A-205992503, indicating its severity and the need for immediate remediation across affected device fleets. The memory corruption resulting from this out of bounds write can potentially lead to system instability, arbitrary code execution, or complete system compromise, depending on how the corrupted memory is utilized by the kernel during subsequent operations.