CVE-2018-21070 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.x), O(8.0) devices (MSM8998 or SDM845 chipsets) software. An attacker can bypass Secure Boot and obtain root access because of a missing Bootloader integrity check. The Samsung ID is SVE-2018-11552 (May 2018).
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Analysis
by VulDB Data Team • 10/07/2020
This vulnerability represents a critical failure in the hardware security architecture of Samsung mobile devices running Android Nougat 7.x and Oreo 8.0 operating systems. The issue specifically affects devices equipped with Qualcomm MSM8998 or SDM845 chipsets, which are commonly found in high-end smartphones and tablets from 2017-2018. The vulnerability stems from a fundamental flaw in the Secure Boot implementation where the bootloader fails to properly validate the integrity of the boot process, creating an exploitable gap in the device's security chain.
The technical flaw manifests as a missing Bootloader integrity check that should normally verify the authenticity and integrity of all boot components before execution. This missing validation allows an attacker to replace or modify the bootloader with a malicious version that can bypass all subsequent security measures. The vulnerability operates at the lowest level of the device's security architecture, making it particularly dangerous because it undermines the foundation upon which all other security mechanisms depend. This type of vulnerability maps directly to CWE-1107, which describes weaknesses in the implementation of secure boot mechanisms, specifically the absence of proper integrity checks in the boot process.
The operational impact of this vulnerability is severe and far-reaching, as it enables attackers to achieve persistent root access on affected devices without requiring any user interaction or physical access to the device. Once exploited, the attacker gains complete control over the device's operating system and can install malicious software, extract sensitive data, or monitor user activities. The vulnerability affects a significant number of devices since MSM8998 and SDM845 chipsets were widely deployed across Samsung's flagship lineup during 2017-2018, including popular models such as the Galaxy S8, S8+, and Note 8. This widespread deployment increases the potential attack surface and makes the vulnerability particularly attractive to threat actors.
From an attack perspective, this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, specifically those related to privilege escalation and persistence. The exploitation process typically involves leveraging the bootloader bypass to install a custom recovery or modified boot image, which then provides the attacker with root-level access to the device. This access enables further exploitation techniques such as installing backdoors, modifying system files, or extracting encryption keys from the device's secure element. The vulnerability also relates to ATT&CK technique T1068, which covers local privilege escalation, and T1543, which covers creation of persistence mechanisms through boot or logon initialization scripts.
The recommended mitigations for this vulnerability include immediate installation of Samsung's security patches and firmware updates that restore the missing bootloader integrity checks. Organizations should implement device management policies that enforce timely security updates and monitor for unauthorized modifications to device firmware. Network administrators should consider implementing mobile device management solutions that can detect and prevent exploitation attempts. Additionally, users should be educated about the risks of installing unofficial firmware or rooting their devices, as these actions can make them more vulnerable to exploitation of this and similar vulnerabilities. The fix typically involves updating the bootloader firmware to properly validate all boot components before execution, ensuring that only authenticated and verified code can proceed with the boot process. This vulnerability highlights the critical importance of hardware-level security implementations and demonstrates how weaknesses at the bootloader level can compromise entire device security architectures.