CVE-2017-5624 in OxygenOS
Summary
by MITRE
An issue was discovered in OxygenOS before 4.0.3 for OnePlus 3 and 3T. The attacker can persistently make the (locked) bootloader start the platform with dm-verity disabled, by issuing the 'fastboot oem disable_dm_verity' command. Having dm-verity disabled, the kernel will not verify the system partition (and any other dm-verity protected partition), which may allow for persistent code execution and privilege escalation.
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Analysis
by VulDB Data Team • 09/06/2020
The vulnerability described in CVE-2017-5624 represents a critical security flaw in OxygenOS versions prior to 4.0.3 affecting OnePlus 3 and 3T devices. This issue stems from an insecure implementation of the fastboot oem disable_dm_verity command that allows attackers to bypass the Android Verified Boot mechanism. The flaw exists at the bootloader level where proper authentication and authorization checks are missing, enabling any attacker with physical access to the device to disable crucial security protections. This vulnerability is particularly concerning as it operates at a fundamental level of device security, affecting the core integrity verification mechanisms that protect against unauthorized modifications.
The technical implementation of this vulnerability involves the exploitation of the fastboot protocol's OEM commands, specifically targeting the dm-verity verification mechanism that is designed to ensure the integrity of system partitions. When the 'fastboot oem disable_dm_verity' command is executed, it permanently disables the dm-verity checks that would normally prevent modification of the system partition. This creates a persistent backdoor that remains active even after device reboots, as the bootloader configuration is modified in a way that survives normal system operations. The vulnerability is classified under CWE-284 Access Control, specifically related to insufficient privileges for critical system functions, and represents a failure in the principle of least privilege enforcement.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to achieve persistent code execution and privilege escalation without requiring sophisticated attack vectors or network access. Once dm-verity is disabled, attackers can install malicious code that will not be detected by the system's integrity verification mechanisms, effectively providing root access to the device. This capability allows for complete system compromise, data exfiltration, and the installation of persistent malware that can survive device reboots. The vulnerability directly aligns with ATT&CK technique T1610 Privilege Escalation through Boot or Logon Initialization Scripts and T1068 Local Privilege Escalation, as it provides a pathway for attackers to gain elevated system privileges through bootloader manipulation.
Mitigation strategies for this vulnerability primarily involve updating to OxygenOS 4.0.3 or later versions where the bootloader security has been strengthened to prevent unauthorized disabling of dm-verity. Device manufacturers should implement proper authentication mechanisms for OEM commands and enforce strict access controls on bootloader configuration modifications. Additionally, users should be educated about the risks of enabling USB debugging or fastboot modes in production environments, as these features can facilitate exploitation of similar vulnerabilities. Security researchers and organizations should monitor for similar issues in bootloader implementations and ensure that all system-level security mechanisms maintain proper enforcement of integrity checks. The vulnerability serves as a reminder of the critical importance of securing bootloader interfaces and maintaining proper access controls at the lowest levels of device security architecture.