CVE-2019-20557 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 SIM card by blocking the PUK code. The Samsung ID is SVE-2019-15262 (October 2019).
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Analysis
by VulDB Data Team • 10/04/2020
The vulnerability described in CVE-2019-20557 represents a critical security flaw in Samsung mobile devices running Android versions 7.x, 8.x, and 9.0. This issue specifically targets the Factory Reset Protection mechanism that is designed to prevent unauthorized access to devices after a factory reset operation. The flaw allows attackers to circumvent the FRP protection by exploiting the SIM card PUK code blocking functionality, effectively undermining one of the primary security measures designed to protect user data and device integrity. The vulnerability was identified and documented by Samsung under their internal security tracking system as SVE-2019-15262, with the disclosure occurring in October 2019, highlighting the sophisticated nature of the attack vector that leverages the device's SIM card management system.
The technical implementation of this vulnerability stems from how Samsung's FRP implementation interacts with SIM card status indicators during device boot and reset processes. When a device attempts to perform a factory reset, the FRP mechanism typically requires authentication through the user's Samsung account credentials to prevent unauthorized access. However, the flaw allows attackers to manipulate the SIM card PUK code blocking state to trick the device into bypassing this authentication requirement. This occurs because the device's security logic fails to properly validate the SIM card state when the PUK code is blocked, creating an exploitable condition that can be leveraged to gain access to the device without proper authorization. The vulnerability specifically exploits a weakness in the device's boot process where it does not adequately verify the legitimacy of the SIM card state before proceeding with FRP validation.
The operational impact of this vulnerability extends beyond simple device access compromise, as it fundamentally undermines the security model that Samsung has implemented to protect user data. An attacker who successfully exploits this vulnerability can potentially access all data stored on the device, including personal information, messages, photos, and applications, without needing the legitimate user's credentials. This creates a significant risk for users who rely on their mobile devices for sensitive information storage and communication. The vulnerability is particularly concerning because it affects multiple Android versions and device models, indicating a widespread implementation flaw that would require extensive patching across Samsung's product portfolio. The attack vector through SIM card manipulation makes this vulnerability particularly insidious as it can be executed without requiring physical access to the device or specialized equipment beyond basic mobile network infrastructure knowledge.
The security implications of this vulnerability align with common attack patterns identified in the MITRE ATT&CK framework, specifically relating to privilege escalation and credential access techniques. The flaw represents a bypass of device-level security controls that would typically fall under the category of 'Exploitation for Privilege Escalation' within the ATT&CK methodology. From a CWE perspective, this vulnerability corresponds to CWE-284, which deals with improper access control, and potentially CWE-312, which addresses exposure of sensitive information through improper handling of authentication mechanisms. The vulnerability demonstrates how improper validation of device state information can create security gaps in mobile device protection mechanisms. Organizations and individuals should consider this vulnerability as part of their broader mobile security risk assessment, particularly when implementing bring-your-own-device policies or managing corporate mobile device fleets where such bypass techniques could be exploited to gain unauthorized access to sensitive corporate data.
Mitigation strategies for this vulnerability should include immediate software updates from Samsung to address the specific FRP bypass mechanism. Users should ensure their devices are running the latest security patches available through Samsung's official update channels, as the vulnerability was patched in subsequent software releases. Device administrators should implement additional security measures such as enabling encryption, using strong authentication methods, and establishing clear policies regarding device reset procedures. Organizations should consider implementing mobile device management solutions that can monitor for unauthorized reset attempts and provide additional layers of protection beyond the device's native security features. The vulnerability also highlights the importance of proper security testing for mobile device boot processes and authentication mechanisms, particularly those involving multiple authentication factors and state validation checks. Regular security audits of device firmware and operating system components should be conducted to identify similar implementation flaws that could compromise device security.