CVE-2018-16658 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 4.18.6. An information leak in cdrom_ioctl_drive_status in drivers/cdrom/cdrom.c could be used by local attackers to read kernel memory because a cast from unsigned long to int interferes with bounds checking. This is similar to CVE-2018-10940.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16658 represents a critical information disclosure flaw within the Linux kernel version prior to 4.18.6. This issue resides in the cdrom_ioctl_drive_status function located in the drivers/cdrom/cdrom.c file, where a fundamental type casting error creates an exploitable condition that allows local attackers to access sensitive kernel memory contents. The flaw manifests due to improper handling of data types during ioctl command processing for CD-ROM devices, creating a pathway for unauthorized memory reading that could expose confidential system information.
The technical root cause of this vulnerability stems from a type conversion error where an unsigned long value is cast to an int type, which subsequently interferes with proper bounds checking mechanisms. This casting operation creates a scenario where the kernel fails to properly validate input parameters, allowing an attacker to manipulate the ioctl interface to read beyond intended memory boundaries. The vulnerability is particularly concerning because it operates at the kernel level where memory addresses and system internals are accessible, potentially exposing sensitive data including cryptographic keys, passwords, or other confidential information stored in kernel memory spaces.
This information leak vulnerability operates within the context of local privilege escalation attacks and can be classified under CWE-200 (Information Exposure) and CWE-128 (Wrap or Overflow) categories. The flaw enables attackers to potentially extract kernel memory contents through carefully crafted ioctl commands, which could reveal system configuration details, memory layout information, or other sensitive data that could be leveraged for further exploitation. The similarity to CVE-2018-10940 indicates this represents a broader pattern of type casting issues in kernel device drivers that compromise memory safety mechanisms.
The operational impact of CVE-2018-16658 extends beyond simple information disclosure, as the leaked kernel memory could contain critical system information that aids in advanced exploitation techniques. Attackers could potentially use the leaked information to bypass security mechanisms such as kernel address space layout randomization or to identify specific kernel versions and configurations. This vulnerability particularly affects systems running Linux kernel versions earlier than 4.18.6, making it a significant concern for organizations maintaining older kernel versions or those that have not implemented proper patch management procedures.
Mitigation strategies for this vulnerability primarily involve upgrading to Linux kernel version 4.18.6 or later where the type casting issue has been resolved through proper bounds checking implementation. System administrators should prioritize patching affected systems and implementing monitoring for suspicious ioctl activity related to CD-ROM devices. Additionally, organizations should consider implementing kernel lockdown mechanisms and restricting local user access to CD-ROM devices when possible. The fix typically involves correcting the unsigned long to int casting operation to maintain proper bounds checking and prevent unauthorized memory access through the ioctl interface, aligning with security best practices recommended by the ATT&CK framework for kernel-level defense mechanisms.