CVE-2019-20602 in Samsung
Summary
by MITRE
An issue was discovered on Samsung mobile devices with N(7.x), O(8.0), and P(9.0) (Qualcomm chipsets) software. The Authnr Trustlet has a NULL pointer dereference. The Samsung ID is SVE-2019-13949 (May 2019).
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Analysis
by VulDB Data Team • 10/04/2020
The vulnerability identified as CVE-2019-20602 represents a critical NULL pointer dereference flaw within the Authnr Trustlet component of Samsung mobile devices running Android versions 7.x, 8.0, and 9.0 that utilize Qualcomm chipsets. This issue specifically affects the secure element communication stack where the Authnr Trustlet serves as a critical security component responsible for authenticating user credentials and managing cryptographic operations. The vulnerability stems from inadequate input validation within the trustlet's processing logic, where the system fails to properly validate pointer references before dereferencing them. This flaw exists in the Samsung proprietary security implementation that interfaces with Qualcomm's TrustZone technology, creating a potential attack vector that could compromise the device's secure boot process and authentication mechanisms. The vulnerability was assigned the Samsung ID SVE-2019-13949 and was disclosed in May 2019, indicating it was present in the security ecosystem for several months before public awareness.
The technical implementation of this vulnerability occurs when the Authnr Trustlet receives malformed or unexpected input data during authentication operations, particularly when processing user credentials or cryptographic tokens. The trustlet's code fails to perform proper null checks on pointer variables before attempting to access memory locations, leading to a system crash or potential code execution. This NULL pointer dereference can be triggered through specially crafted authentication requests or by exploiting weaknesses in the communication protocol between the application processor and the secure element. The flaw resides in the trustlet's memory management routines where it assumes certain pointers will always contain valid addresses, but due to improper validation, these assumptions can be violated. According to CWE classification, this vulnerability maps to CWE-476 which describes NULL Pointer Dereference, a well-known weakness that can lead to system instability and potential privilege escalation. The attack surface is particularly concerning as it affects the core authentication infrastructure that protects sensitive user data and device security credentials.
The operational impact of this vulnerability extends beyond simple system instability, potentially enabling attackers to gain unauthorized access to secure device functions and compromise the integrity of the authentication system. An attacker could exploit this vulnerability to cause denial of service conditions, forcing the device into a reboot cycle that could disrupt legitimate user operations. More critically, the vulnerability could be leveraged to bypass authentication mechanisms or to execute malicious code within the secure execution environment, particularly since the trustlet operates with elevated privileges and access to cryptographic keys. The implications are significant given that the affected devices operate on Qualcomm chipsets that are widely deployed across the mobile ecosystem, potentially affecting millions of users. This vulnerability aligns with ATT&CK technique T1068 which involves exploiting legitimate credentials or system privileges to gain access to secure environments, and T1134 which covers access token manipulation in secure contexts. The risk is amplified by the fact that the trustlet operates in a trusted execution environment where the system assumes all operations are legitimate and secure.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security hardening measures. Samsung issued security patches for affected devices, but users should ensure their devices are updated to the latest security releases that contain fixes for this NULL pointer dereference. The patch typically involves implementing proper null checks and input validation within the Authnr Trustlet code before any pointer dereference operations occur. System administrators and security teams should monitor for exploitation attempts and implement network-based intrusion detection systems to identify potential attack patterns targeting this specific vulnerability. Device manufacturers should enhance their secure element communication protocols to include additional validation layers and implement more robust error handling mechanisms. The vulnerability highlights the importance of secure coding practices in trusted execution environments and reinforces the need for thorough security testing of components that operate in sensitive security contexts. Organizations should also consider implementing device integrity monitoring solutions that can detect abnormal behavior patterns associated with trustlet exploitation attempts. The fix typically requires code-level modifications to ensure all pointer variables are validated before use, preventing the exploitation pathway that leads to the NULL pointer dereference condition.