CVE-2018-5890 in Android
Summary
by MITRE
If the fdt_totalsize is reported as 0 for the current device tree, it bypasses an error check for a valid device tree in Android releases from CAF using the linux kernel (Android for MSM, Firefox OS for MSM, QRD Android) before security patch level 2018-06-05.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/05/2023
The vulnerability described in CVE-2018-5890 represents a critical flaw in the Android kernel's device tree handling mechanism that affects multiple Android for MSM platforms. This issue specifically targets the Fastboot Download (fdt) subsystem where the device tree total size parameter is used to validate the integrity and legitimacy of device tree blobs. When the fdt_totalsize field reports a value of zero, the system bypasses crucial validation checks that should ensure the device tree contains valid and properly structured data. This vulnerability exists in Android releases from the Code Aurora Forum (CAF) that utilize the Linux kernel, affecting platforms including Android for MSM, Firefox OS for MSM, and QRD Android implementations.
The technical flaw manifests in the kernel's device tree validation logic where the zero value check for fdt_totalsize serves as an insufficient validation mechanism. This allows attackers to potentially inject malformed device tree data that would normally be rejected by proper validation routines. The vulnerability operates at the kernel level during the early boot process when device tree information is processed, making it particularly dangerous as it can affect system initialization and potentially provide attack vectors for privilege escalation or system compromise. The flaw represents a classic case of insufficient input validation where a null or zero value bypasses security checks that should prevent malformed data from being processed.
The operational impact of this vulnerability is significant as it creates potential pathways for attackers to manipulate the device tree during the boot process, which can lead to various security consequences including but not limited to unauthorized system modifications, privilege escalation, and potential complete system compromise. Attackers could exploit this vulnerability by crafting device tree blobs with zero totalsize values to bypass validation checks, potentially allowing them to inject malicious code or manipulate system behavior before normal security mechanisms are fully initialized. The vulnerability affects devices running before the 2018-06-05 security patch level, making a substantial portion of Android devices susceptible to this attack vector.
This vulnerability aligns with CWE-20, which describes improper input validation, and can be mapped to ATT&CK technique T1068, which involves exploiting legitimate credentials and privileges. The issue demonstrates how seemingly benign parameter values can bypass critical security checks, creating a pathway for attackers to manipulate kernel-level data structures. The vulnerability specifically impacts the Android kernel's device tree handling and can be exploited during the boot process when the system initializes device tree information. Organizations should implement immediate mitigations including applying the security patches released on or after 2018-06-05, and conducting thorough device tree validation checks to ensure that all device tree blobs contain valid and properly structured data. Additionally, system administrators should monitor for any unauthorized modifications to device tree configurations and implement proper device tree integrity verification mechanisms to prevent exploitation of this vulnerability.