CVE-2021-25481 in Exynos CP Booting Driver
Summary
by MITRE • 10/06/2021
An improper error handling in Exynos CP booting driver prior to SMR Oct-2021 Release 1 allows local attackers to bypass a Secure Memory Protector of Exynos CP Memory.
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Analysis
by VulDB Data Team • 10/10/2021
The vulnerability identified as CVE-2021-25481 represents a critical flaw in the Exynos CP booting driver architecture that affects Samsung mobile devices utilizing the Exynos chipset. This issue stems from inadequate error handling mechanisms within the boot process, specifically targeting the Secure Memory Protector (SMP) functionality designed to safeguard sensitive memory regions. The vulnerability exists in versions prior to the SMR October 2021 Release 1, indicating that Samsung had not yet addressed this security weakness in their firmware updates. The Secure Memory Protector is a fundamental security feature that prevents unauthorized access to critical system memory areas containing sensitive data and code execution paths, making this flaw particularly concerning for mobile device security.
The technical implementation of this vulnerability involves a failure in the driver's error handling routines during the boot sequence when processing memory protection mechanisms. When the Exynos CP booting driver encounters certain error conditions, it fails to properly validate or enforce memory protection boundaries, allowing malicious code or processes to access memory regions that should remain protected. This improper error handling creates a pathway for local attackers to manipulate the system's memory protection mechanisms, effectively undermining the core security architecture designed to isolate critical components. The flaw specifically targets the interaction between the booting driver and the Secure Memory Protector, where error conditions should trigger protective measures but instead result in weakened security states.
From an operational perspective, this vulnerability enables local attackers with physical access or code execution capabilities to bypass memory protection mechanisms that are essential for maintaining system integrity. The implications extend beyond simple privilege escalation, as attackers can potentially access sensitive data, modify critical system components, or establish persistent backdoors within the device's memory space. The vulnerability is particularly dangerous because it operates at the boot level, meaning it can affect the entire system security posture from the earliest stages of device operation. Attackers could leverage this flaw to gain access to cryptographic keys, secure storage areas, or other sensitive information that should remain protected by the Secure Memory Protector. This represents a significant weakening of the device's security model, as the fundamental memory protection mechanisms fail during the most critical phase of system initialization.
The vulnerability aligns with CWE-252, which addresses "Unchecked Return Value," and demonstrates how inadequate error handling can lead to security weaknesses in system components. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and defense evasion, as it allows attackers to bypass security controls that should prevent unauthorized memory access. The security implications suggest that this flaw could be exploited in conjunction with other attack vectors to establish persistent access or escalate privileges within the device's operating environment. Organizations and users should prioritize updating to the SMR October 2021 Release 1 or later versions that contain the necessary patches for this vulnerability. Additionally, system administrators should implement monitoring for unusual memory access patterns that could indicate exploitation attempts. The remediation approach requires proper error handling implementation in the booting driver to ensure that all error conditions properly enforce memory protection boundaries rather than inadvertently weakening them.