CVE-2021-39677 in Android
Summary
by MITRE • 02/11/2022
In startVideoStream() there is a possibility of an OOB Read in the heap, when the camera buffer is ‘zero’ in size.Product: AndroidVersions: Android-11Android ID: A-205097028
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Analysis
by VulDB Data Team • 02/17/2022
The vulnerability identified as CVE-2021-39677 represents a critical out-of-bounds read condition within the Android operating system's video streaming functionality. This issue manifests specifically within the startVideoStream() method where the system attempts to process camera buffer data that has been allocated with zero size. The flaw exists in Android 11 and is tracked under Android ID A-205097028, indicating its significance within the Android security framework. The vulnerability stems from inadequate input validation and buffer size checking mechanisms that fail to properly handle edge cases where camera buffer allocation results in null or zero-sized buffers.
The technical implementation of this vulnerability involves heap memory access patterns that do not properly validate the size parameter of camera buffers before attempting to read from them. When the camera buffer is initialized with zero size, the system continues to attempt memory operations that expect valid buffer dimensions, leading to unauthorized heap memory access. This type of vulnerability falls under CWE-129, which specifically addresses insufficient input validation, and more broadly aligns with CWE-125, describing out-of-bounds read conditions. The flaw demonstrates a classic buffer overflow pattern where the system fails to check array bounds before memory access operations, creating potential for information disclosure or system instability.
From an operational perspective, this vulnerability presents significant security implications for Android devices running Android 11. An attacker could potentially exploit this condition to read sensitive data from adjacent heap memory locations, potentially accessing credentials, personal information, or other confidential data stored in memory. The vulnerability is particularly concerning because it occurs during video streaming operations, which are frequently used and may be accessible to malicious applications or exploited through compromised user interactions. The attack surface extends to any application that utilizes the Android camera API for video streaming functionality, making this a widespread potential threat across numerous Android applications and device configurations.
Mitigation strategies for CVE-2021-39677 should focus on implementing comprehensive buffer size validation within the startVideoStream() method and related camera buffer handling functions. System administrators and developers should ensure that all camera buffer allocations are verified for valid size parameters before any memory operations are performed. The Android security team has addressed this vulnerability through patch updates that include proper input validation and boundary checking mechanisms. Organizations should implement immediate security updates and monitor for any exploitation attempts. Additionally, the implementation of runtime application security controls and memory protection mechanisms such as stack canaries and address space layout randomization can provide additional defense-in-depth measures. This vulnerability also highlights the importance of adhering to secure coding practices and following ATT&CK framework guidelines for mobile application security, particularly in the area of mobile application memory management and input validation controls.