CVE-2017-8239 in Android
Summary
by MITRE
In all Android releases from CAF using the Linux kernel, userspace-controlled parameters for flash initialization are not sanitized potentially leading to exposure of kernel memory.
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Analysis
by VulDB Data Team • 12/27/2020
This vulnerability exists within the Android operating system's kernel implementation where userspace applications can provide parameters that control flash memory initialization processes. The flaw stems from inadequate input validation and sanitization mechanisms that allow malicious or malformed parameters to be passed directly to kernel space without proper verification. When flash memory devices are initialized, the kernel processes these parameters to configure memory attributes and access controls. However, the absence of proper parameter sanitization creates a path where userspace-controlled data can influence kernel memory operations, potentially exposing sensitive kernel memory contents to unauthorized access.
The technical implementation of this vulnerability involves the interaction between userspace applications and kernel drivers responsible for flash memory management. When applications request flash memory initialization, they pass parameters that define memory regions, access permissions, and initialization sequences. These parameters are typically validated in userspace before being transmitted to kernel space, but in this case, the validation process is insufficient or completely absent. The vulnerability allows for parameter manipulation that can result in kernel memory disclosure, where sensitive data structures, kernel addresses, or other confidential information may be read by userspace processes. This represents a classic case of insufficient input sanitization that can lead to information disclosure and potential privilege escalation scenarios.
The operational impact of CVE-2017-8239 is significant within the Android ecosystem, particularly affecting devices running Android versions that utilize the Linux kernel implementation from Code Aurora Forum. Attackers can exploit this vulnerability by crafting malicious parameters that, when passed to flash initialization functions, cause the kernel to expose memory contents. This exposure can reveal kernel memory layouts, sensitive data structures, or other confidential information that could be leveraged for further attacks. The vulnerability affects a broad range of Android devices since it impacts all versions using the affected kernel implementation, making it a widespread concern across multiple device manufacturers and software versions. The information disclosure aspect of this vulnerability can enable attackers to perform advanced exploitation techniques such as kernel address space layout randomization (ASLR) bypasses or heap spraying attacks.
Mitigation strategies for this vulnerability primarily focus on implementing proper input validation and sanitization mechanisms within kernel space. The recommended approach involves adding comprehensive parameter validation checks before any userspace-provided parameters are processed by kernel drivers. This includes implementing bounds checking, type validation, and memory access restrictions to prevent malicious parameter manipulation from affecting kernel memory operations. Security patches typically involve modifying kernel drivers to sanitize all userspace-controlled parameters before they are used in flash memory initialization processes. Additionally, implementing proper kernel memory protection mechanisms such as kernel address space layout randomization, stack canaries, and other exploit mitigations can help reduce the overall impact of such vulnerabilities. Organizations should also consider implementing monitoring and logging of flash initialization operations to detect potential exploitation attempts and maintain compliance with security standards such as those outlined in the CWE taxonomy under weakness category 707 for improper neutralization of components.
This vulnerability aligns with several ATT&CK techniques including privilege escalation through kernel exploits and information gathering via memory disclosure attacks. The weakness classification places this issue under CWE-20, which covers improper input validation, and CWE-125, which addresses out-of-bounds read conditions. The exploitation of this vulnerability demonstrates the importance of defense in depth approaches in kernel security, where multiple layers of protection are necessary to prevent unauthorized access to sensitive kernel memory areas. Device manufacturers and security researchers should prioritize patch deployment and ongoing monitoring of similar vulnerabilities in kernel implementations to maintain robust security postures across Android ecosystems.