CVE-2021-0956 in Android
Summary
by MITRE • 12/15/2021
In NfcTag::discoverTechnologies (activation) of NfcTag.cpp, there is a possible out of bounds write due to an incorrect bounds check. This could lead to remote escalation of privilege with no additionalSystem execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-11 Android-12Android ID: A-189942532
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-0956 represents a critical out-of-bounds write flaw within the Android NFC subsystem, specifically within the NfcTag::discoverTechnologies function located in NfcTag.cpp. This issue manifests during the activation phase of NFC tag discovery operations, where improper bounds checking allows for memory corruption that can be exploited to achieve privilege escalation. The vulnerability affects Android versions 11 and 12, making it particularly concerning given the widespread adoption of these operating systems across mobile devices and IoT applications. The flaw operates at the kernel level within the NFC framework, leveraging the inherent trust placed in NFC operations to execute malicious code with elevated privileges.
The technical implementation of this vulnerability stems from inadequate validation of array bounds during NFC technology discovery processes. When the NFC subsystem attempts to identify supported technologies on a tag, the NfcTag::discoverTechnologies function fails to properly validate the size of data structures before writing to memory locations. This incorrect bounds checking creates a scenario where an attacker can manipulate NFC tag data to overwrite adjacent memory regions, potentially corrupting critical system structures or executing arbitrary code. The vulnerability's classification as a remote exploit means that malicious actors can trigger the condition without physical access to the device, making it particularly dangerous in mobile environments where NFC is frequently used for transactions and device interactions. The flaw falls under CWE-787 Out-of-bounds Write, which is categorized as a direct consequence of insufficient bounds checking mechanisms in memory operations.
The operational impact of CVE-2021-0956 extends beyond simple privilege escalation to encompass potential system compromise and data exfiltration capabilities. An attacker exploiting this vulnerability can gain root-level access to affected Android devices, enabling them to modify system files, install malicious applications, monitor communications, and access sensitive user data without requiring any user interaction or additional privileges. This remote exploitation capability makes the vulnerability particularly attractive to threat actors targeting mobile devices for financial gain, espionage, or network infiltration. The attack surface is broadened by the ubiquitous nature of NFC functionality in modern smartphones, where users frequently interact with NFC-enabled payment systems, smart locks, and device pairing operations, creating multiple potential entry points for exploitation. The vulnerability's presence in Android 11 and 12 versions means that a significant portion of the mobile ecosystem remains at risk, with millions of devices potentially vulnerable to this attack vector.
Mitigation strategies for CVE-2021-0956 primarily focus on immediate system updates and patch management, with Android security updates addressing the underlying bounds checking implementation in the NFC subsystem. Organizations should prioritize deployment of the latest security patches from Google, which include enhanced bounds validation and memory protection mechanisms within the NFC framework. System administrators should also implement network monitoring solutions to detect anomalous NFC activity patterns that might indicate exploitation attempts, while security teams should conduct thorough vulnerability assessments of NFC-dependent applications and services. The mitigation approach aligns with ATT&CK technique T1068, which addresses privilege escalation through local exploitation, and emphasizes the importance of maintaining up-to-date system firmware and implementing robust access controls. Additional defensive measures include disabling unnecessary NFC functionality when not required, implementing mobile device management policies that enforce security updates, and conducting regular security audits of NFC-enabled applications to ensure proper input validation and memory handling practices. The vulnerability serves as a reminder of the critical importance of memory safety in mobile operating systems and the potential consequences of insufficient bounds checking in system-level components.