CVE-2017-15855 in Android
Summary
by MITRE
In Qualcomm Android for MSM, Firefox OS for MSM, and QRD Android with all Android releases from CAF using the Linux kernel, the camera application triggers "user-memory-access" issue as the Camera CPP module Linux driver directly accesses the application provided buffer, which resides in user space. An unchecked userspace value (ioctl_ptr->len) is used to copy contents to a kernel buffer which can lead to kernel buffer overflow.
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Analysis
by VulDB Data Team • 02/07/2020
The vulnerability identified as CVE-2017-15855 represents a critical security flaw affecting Qualcomm Android devices, Firefox OS for MSM, and QRD Android systems utilizing Linux kernel components. This issue stems from improper memory management within the camera application's interaction with the Camera CPP module Linux driver, creating a dangerous pathway for privilege escalation and system compromise. The flaw manifests when the kernel driver directly accesses user-space buffers provided by the camera application, establishing a direct interface between untrusted user data and kernel memory operations.
The technical implementation of this vulnerability involves a specific memory access pattern where the kernel driver processes application-provided buffer lengths without adequate validation or bounds checking. The ioctl_ptr->len parameter, which represents the buffer length supplied by the user-space application, is directly used to determine the copy size for kernel buffer operations. This unchecked value serves as the primary attack vector, allowing malicious actors to manipulate the buffer size parameter and potentially trigger a kernel buffer overflow condition. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, though it specifically operates within kernel space rather than user space, making it particularly dangerous due to the elevated privileges of kernel operations.
The operational impact of this vulnerability extends far beyond simple data corruption, as it enables attackers to gain unauthorized access to kernel memory regions and potentially execute arbitrary code with the highest system privileges. An attacker exploiting this flaw could manipulate the camera application to send malicious buffer size parameters that exceed kernel buffer boundaries, leading to memory corruption that might result in system crashes, privilege escalation, or complete system compromise. The vulnerability affects all Android releases from CAF using the Linux kernel, indicating a widespread exposure across multiple device platforms and manufacturers. This issue directly aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation," and T1059, covering "Command and Scripting Interpreter," as successful exploitation could enable attackers to execute arbitrary commands with kernel-level privileges.
Mitigation strategies for CVE-2017-15855 require immediate patching of affected kernel versions and implementation of proper input validation mechanisms within the camera driver components. System administrators should prioritize updating devices to versions containing kernel patches that implement proper bounds checking for buffer length parameters before kernel memory operations. The fix typically involves adding validation checks to ensure that user-provided buffer sizes do not exceed maximum allowable kernel buffer dimensions, thereby preventing the buffer overflow condition. Additionally, implementing kernel memory protection features such as stack canaries, address space layout randomization, and kernel address space layout randomization can provide additional defense-in-depth measures. Organizations should also consider monitoring for anomalous camera application behavior and implementing network-based intrusion detection systems to identify potential exploitation attempts. The vulnerability highlights the importance of secure coding practices in kernel drivers and demonstrates the critical need for proper input validation when interfacing between user-space applications and kernel memory regions, particularly in mobile device security contexts where such interfaces are common.