CVE-2017-9721 in Android
Summary
by MITRE
In android for MSM, Firefox OS for MSM, QRD Android, with all Android releases from CAF using the Linux kernel, in the boot loader, a buffer overflow can occur while parsing the splash image.
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Analysis
by VulDB Data Team • 12/07/2019
The vulnerability identified as CVE-2017-9721 represents a critical buffer overflow condition affecting multiple Android-based platforms including MSM variants, Firefox OS for MSM, and QRD Android implementations. This flaw exists within the bootloader component of these systems and specifically manifests during the parsing of splash images which are typically displayed during device boot sequences. The vulnerability stems from inadequate input validation mechanisms within the bootloader code that processes splash image data structures without proper bounds checking. This allows malicious actors to craft specially crafted splash images that can trigger memory corruption when the bootloader attempts to parse these images during the boot process.
The technical nature of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and potentially CWE-787, representing out-of-bounds write vulnerabilities. The attack surface is particularly concerning as it operates at the bootloader level, which is one of the earliest components executed during system boot and typically runs with the highest privileges. This positioning makes the vulnerability particularly dangerous as it can be exploited before the operating system security mechanisms are fully initialized. The exploitation of this vulnerability can potentially lead to arbitrary code execution within the bootloader context, which provides attackers with a powerful foothold for system compromise.
From an operational impact perspective, this vulnerability affects all Android releases from the Code Aurora Forum (CAF) that utilize the Linux kernel and operate on MSM-based hardware platforms. The implications extend beyond simple system instability as successful exploitation could enable attackers to bypass secure boot mechanisms, modify bootloader code, or install persistent backdoors. The vulnerability is particularly concerning in environments where physical access to devices is possible, as attackers could craft malicious splash images and deploy them through various attack vectors including compromised update channels or direct device manipulation. The exploitation typically requires the attacker to have control over the splash image content, making it a supply chain or physical access attack vector rather than a network-based vulnerability.
The mitigation strategies for CVE-2017-9721 should focus on both immediate and long-term solutions. Immediate remediation involves updating the bootloader firmware to versions that include proper bounds checking and input validation for splash image parsing. Organizations should implement secure boot policies that verify the integrity of bootloader components and splash images before execution. The ATT&CK framework categorizes this type of vulnerability under T1068, which describes "Exploitation for Privilege Escalation" and T1542, covering "Pre-OS Boot" techniques. System administrators should also consider implementing hardware-based security measures such as Trusted Platform Modules (TPMs) and secure boot mechanisms to prevent unauthorized bootloader modifications. Additionally, regular security assessments of boot processes and firmware updates should be mandated to address similar vulnerabilities that may be discovered in the future. The vulnerability highlights the importance of secure boot chain implementation and proper input validation at all levels of system execution, particularly in early boot components where traditional security controls may not yet be active.