CVE-2021-0640 in Android
Summary
by MITRE • 08/17/2021
In noteAtomLogged of StatsdStats.cpp, there is a possible out of bounds write due to a missing bounds check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-10 Android-11 Android-9Android ID: A-187957589
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Analysis
by VulDB Data Team • 08/20/2021
The vulnerability identified as CVE-2021-0640 resides within the Android system's statsd component, specifically in the noteAtomLogged function located in StatsdStats.cpp. This flaw represents a critical out-of-bounds write condition that stems from the absence of proper bounds checking mechanisms. The affected Android versions include Android 9, Android 10, and Android 11, indicating a widespread impact across multiple system generations. The vulnerability occurs within the statsd daemon which is responsible for collecting and reporting system statistics, making it a core component of the Android operating system's monitoring infrastructure.
The technical implementation of this vulnerability involves a scenario where the noteAtomLogged function fails to validate array boundaries before writing data to memory locations. When the statsd service processes incoming statistical data, it attempts to store atom information without verifying that the destination buffer can accommodate the incoming data. This missing bounds check creates an opportunity for arbitrary memory corruption that can be exploited to manipulate the system's memory layout. The flaw is particularly concerning because it operates within a privileged context where the statsd service runs with elevated permissions, allowing potential exploitation to result in local privilege escalation. The vulnerability falls under CWE-787 which specifically addresses out-of-bounds write conditions, and aligns with ATT&CK technique T1068 which covers privilege escalation through local exploits.
The operational impact of this vulnerability extends beyond simple memory corruption as it enables local privilege escalation without requiring any additional execution privileges or user interaction. An attacker who gains access to a local account on the device can exploit this flaw to elevate their privileges to system level, effectively compromising the entire device. The lack of user interaction requirement makes this vulnerability particularly dangerous as it can be exploited automatically without the need for social engineering or additional attack vectors. The statsd service typically runs with system privileges, meaning that successful exploitation would grant the attacker complete control over the device's monitoring and statistical data collection mechanisms, potentially allowing for further attacks or data exfiltration.
Mitigation strategies for CVE-2021-0640 primarily focus on updating to patched Android versions where Google has implemented proper bounds checking in the noteAtomLogged function. System administrators should prioritize applying security patches as soon as they become available through official Android update channels. Additional defensive measures include implementing runtime monitoring to detect anomalous memory access patterns and employing application sandboxing techniques to limit the potential impact of exploitation attempts. Organizations should also consider network-level controls to prevent unauthorized local access to affected devices, though the vulnerability's local nature means that physical or administrative access is typically required for exploitation. The fix implemented by Google likely involves adding proper validation checks before array operations and ensuring that all memory writes within the statsd component respect allocated buffer boundaries, aligning with established secure coding practices recommended in both CWE guidelines and industry security frameworks.