CVE-2021-0961 in Android
Summary
by MITRE • 12/15/2021
In quota_proc_write of xt_quota2.c, there is a possible way to read kernel memory due to uninitialized data. 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-196046570References: Upstream kernel
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-0961 resides within the Android kernel's packet filtering subsystem, specifically in the xt_quota2.c module that handles quota processing for netfilter rules. This issue represents a classic information disclosure vulnerability that arises from improper initialization of memory structures during kernel operation. The flaw manifests in the quota_proc_write function where uninitialized data is accessed, potentially exposing sensitive kernel memory contents to unauthorized processes. The vulnerability's classification as a local information disclosure means that an attacker must already possess system execution privileges to exploit it, typically requiring either physical access or prior compromise of a user account with sufficient privileges to execute code within the kernel space.
The technical root cause of this vulnerability stems from the improper handling of uninitialized variables within the kernel's quota processing logic. When the quota_proc_write function processes incoming data, it fails to properly initialize certain memory buffers before accessing them, creating a scenario where residual data from previous operations may be read and potentially exposed. This type of vulnerability falls under the CWE-457 category of "Use of Uninitialized Variable" and represents a fundamental security flaw in kernel memory management practices. The uninitialized data could contain sensitive information such as kernel stack contents, memory addresses, or other confidential data that should remain protected from user-space access. This vulnerability directly impacts the kernel's memory integrity and confidentiality properties, as it allows for the potential leakage of kernel memory contents that could aid in further exploitation attempts.
The operational impact of CVE-2021-0961 is significant within the context of Android device security, particularly for devices running affected kernel versions. While the vulnerability requires system execution privileges for exploitation, this limitation does not diminish its potential threat level in real-world scenarios where attackers may have already compromised user accounts or gained root access through other means. The information disclosure could provide attackers with insights into kernel memory layout, potentially enabling more sophisticated attacks such as kernel address space layout randomization (ASLR) bypass techniques or privilege escalation attempts. The vulnerability's presence in the upstream kernel indicates it affects multiple Android versions and device manufacturers, making it a widespread concern across the Android ecosystem. The fact that this vulnerability has been assigned an Android ID of A-196046570 demonstrates the recognition of its severity by Android security teams and the importance of timely patching.
Mitigation strategies for CVE-2021-0961 primarily involve applying the upstream kernel patches that properly initialize the affected variables within the quota_proc_write function. Device manufacturers and Android developers should prioritize updating kernel versions to include the fix, which typically involves ensuring that all memory buffers are properly initialized before use in kernel space operations. Security researchers and system administrators should monitor for the availability of security patches and apply them promptly to affected systems. The vulnerability's nature makes it particularly susceptible to exploitation in environments where kernel memory analysis is possible, thus making timely patching essential for maintaining system security. Additionally, organizations should consider implementing monitoring solutions that can detect unusual access patterns to kernel memory regions, as this could indicate exploitation attempts. From a defensive perspective, the vulnerability aligns with ATT&CK technique T1068 which involves the use of local privilege escalation techniques, and T1566 which covers the exploitation of vulnerabilities in kernel components, making it a critical target for both proactive security measures and incident response protocols.