CVE-2019-20551 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.x), O(8.x), and P(9.0) software. Attackers can bypass Factory Reset Protection (FRP) via a Class 0 Type Message. The Samsung ID is SVE-2019-14941 (October 2019).
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Analysis
by VulDB Data Team • 10/04/2020
The vulnerability identified as CVE-2019-20551 represents a critical security flaw in Samsung mobile devices running Android versions 7.x, 8.x, and 9.0. This weakness specifically affects the Factory Reset Protection mechanism that is designed to prevent unauthorized use of lost or stolen devices. The issue allows attackers to circumvent the FRP safeguards through the manipulation of Class 0 Type Messages, which are SMS messages that bypass normal messaging protocols and are typically used for emergency alerts and critical system communications. The vulnerability was catalogued under Samsung's internal tracking system as SVE-2019-14941 and was publicly disclosed in October 2019, highlighting the sophisticated nature of the attack vector that targets fundamental device security controls.
The technical implementation of this vulnerability exploits the inherent trust placed in Class 0 SMS messages within the Android messaging framework. These messages are processed with elevated privileges and are designed to be displayed immediately to users without requiring any user interaction or confirmation. Attackers can craft and send malicious Class 0 messages that manipulate the device's FRP state during the boot process or after a factory reset operation. This manipulation occurs because the system fails to properly validate the authenticity and origin of such messages, allowing unauthorized parties to effectively reset the device's protection mechanisms. The flaw resides in the message processing logic that does not adequately verify the integrity of Class 0 messages when they interact with device security protocols, creating a pathway for attackers to gain unauthorized access to protected devices.
The operational impact of this vulnerability extends far beyond simple device compromise, as it fundamentally undermines the security model that Samsung devices rely on for protecting user data and preventing device theft. When an attacker successfully bypasses FRP, they can gain complete access to a device that was previously protected by the manufacturer's security measures, including the ability to access all stored data, installed applications, and personal information. This vulnerability is particularly concerning because it affects devices during their most vulnerable state - immediately after a factory reset when users expect maximum security protection. The attack can be executed remotely without requiring physical access to the device, making it a significant threat to user privacy and data security. According to the ATT&CK framework, this vulnerability aligns with techniques involving privilege escalation and credential access, specifically targeting the device's security initialization processes.
Mitigation strategies for CVE-2019-20551 require both immediate and long-term approaches to address the underlying security flaw. Samsung released security patches that updated the messaging system to properly validate Class 0 messages and prevent their manipulation of FRP states. Users should immediately install all available security updates for their devices, particularly those running Android 7.x, 8.x, and 9.0 versions. Network operators and device manufacturers should implement additional monitoring for suspicious Class 0 message patterns that could indicate exploitation attempts. The vulnerability also highlights the importance of proper input validation and privilege separation in mobile operating systems, as outlined in CWE categories related to improper input validation and privilege escalation. Organizations should consider implementing additional device management policies that restrict messaging capabilities on enterprise devices and maintain awareness of the specific attack patterns associated with this vulnerability. The security community should also monitor for similar vulnerabilities in other mobile platforms that may employ similar messaging protocols and trust models.