CVE-2021-39730 in Android
Summary
by MITRE • 03/16/2022
In TBD of TBD, there is a possible out of bounds read due to a missing bounds check. This could lead to local information disclosure with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-206472503References: N/A
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/19/2022
The vulnerability identified as CVE-2021-39730 represents a critical out-of-bounds read flaw within the Android kernel component, specifically affecting the Tbd subsystem where the vulnerability manifests. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, which directly relates to the absence of proper bounds checking mechanisms that should prevent access to memory locations beyond the allocated array boundaries. The vulnerability exists in the kernel level implementation where insufficient input validation allows malicious code to traverse memory regions that should remain protected, potentially exposing sensitive information to unauthorized access.
The technical implementation of this vulnerability stems from a missing bounds check within the kernel subsystem, creating a scenario where an attacker can manipulate input parameters to cause the system to read memory locations outside of intended buffer boundaries. This flaw operates at the kernel level where system privileges are already granted, meaning that exploitation requires only system execution privileges rather than elevated privileges or complex privilege escalation techniques. The absence of proper validation allows for memory corruption that can reveal kernel memory contents, including potentially sensitive data structures, cryptographic keys, or system configuration information that should remain confidential.
From an operational impact perspective, this vulnerability creates a significant risk for local information disclosure attacks where an attacker with system-level privileges can extract confidential information from kernel memory spaces. The exploitation does not require user interaction, making it particularly dangerous as it can be triggered automatically when the vulnerable subsystem is accessed. The affected Android kernel component represents a fundamental security weakness that could enable adversaries to gain insights into system internals, potentially leading to more sophisticated attacks or targeted exploitation of other system components. This vulnerability directly impacts the confidentiality aspect of the system security model by allowing unauthorized access to kernel memory that should remain protected from local users.
The mitigation strategies for CVE-2021-39730 should focus on implementing comprehensive bounds checking mechanisms within the affected kernel subsystem and ensuring proper input validation at all levels of the software stack. System administrators should prioritize applying security patches provided by Android security teams and kernel maintainers to address the missing validation checks. Additionally, implementing runtime monitoring and memory protection mechanisms such as stack canaries, address space layout randomization, and kernel address space layout randomization can help detect or prevent exploitation attempts. Organizations should also consider implementing least privilege principles and monitoring for unusual memory access patterns that might indicate exploitation attempts. The vulnerability's classification under the ATT&CK framework would fall under the Tactic of Credential Access and Defense Evasion, with techniques potentially including memory injection and information disclosure through kernel-level attacks that leverage the missing bounds checking vulnerability.