CVE-2019-9436 in Android
Summary
by MITRE
In the Android kernel in the bootloader there is a possible secure boot bypass. This could lead to local escalation of privilege with System execution privileges needed. User interaction is needed for exploitation.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-9436 resides within the Android kernel's bootloader component, representing a critical security flaw that undermines the device's secure boot mechanism. This vulnerability specifically affects the bootloader's ability to properly validate the integrity of the boot process, creating a pathway for malicious actors to circumvent the system's security controls. The issue manifests as a secure boot bypass that allows attackers to execute arbitrary code with system-level privileges, fundamentally compromising the device's security architecture. The vulnerability requires user interaction for exploitation, meaning that while the attack vector is not fully automated, it can be triggered through seemingly benign user actions such as connecting a malicious USB device or installing compromised software.
The technical root cause of this vulnerability lies in the bootloader's insufficient validation mechanisms during the boot process, which is classified under CWE-284 - Improper Access Control in the Common Weakness Enumeration catalog. This weakness specifically targets the system's ability to enforce proper access controls during critical boot phases where the system transitions from a trusted state to an operational state. The bootloader's failure to properly authenticate and verify the integrity of boot components creates a window of opportunity for attackers to inject malicious code that can execute with elevated privileges. This flaw directly impacts the Android Security Model's core principle of maintaining a secure boot chain, where each component must cryptographically verify the next component in the boot sequence to prevent unauthorized modifications.
From an operational impact perspective, this vulnerability enables local privilege escalation attacks that can result in complete system compromise. Attackers who successfully exploit this vulnerability can gain system execution privileges, allowing them to bypass all security controls that would normally prevent unauthorized access to sensitive system functions. The requirement for user interaction means that exploitation typically occurs through social engineering or targeted attacks where users are tricked into performing specific actions that trigger the vulnerability. This makes the attack surface more constrained compared to fully automated exploits, but the potential impact remains severe as the attacker can then access all system resources, modify critical files, and potentially establish persistent backdoors. The vulnerability affects devices running Android versions that utilize the affected bootloader implementations, potentially impacting millions of devices across various manufacturers.
Mitigation strategies for CVE-2019-9436 should focus on both immediate remediation and long-term security improvements. Device manufacturers should implement firmware updates that correct the bootloader validation logic and strengthen the secure boot chain implementation. Users should ensure their devices receive timely security updates and avoid connecting untrusted USB devices or installing unknown applications. Security professionals should monitor for exploitation attempts and implement network-based detection measures to identify potential attacks targeting this vulnerability. The mitigation approach aligns with ATT&CK technique T1068 - Exploitation for Privilege Escalation, which specifically addresses the use of system vulnerabilities to gain elevated privileges. Organizations should also consider implementing additional security controls such as device encryption, application whitelisting, and network monitoring to reduce the attack surface and prevent successful exploitation attempts. Regular security assessments of bootloader implementations and secure boot configurations should be conducted to identify similar vulnerabilities and maintain robust security postures.