CVE-2018-18710 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel through 4.19. An information leak in cdrom_ioctl_select_disc 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 and CVE-2018-16658.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability identified as CVE-2018-18710 represents a critical information disclosure flaw within the Linux kernel version 4.19 and earlier. This issue resides in the cdrom_ioctl_select_disc function located in the drivers/cdrom/cdrom.c file, which handles ioctl operations for CD-ROM devices. The flaw manifests as a kernel memory information leak that provides local attackers with unauthorized access to sensitive kernel memory regions. The vulnerability stems from a fundamental type casting error that undermines proper bounds checking mechanisms within the kernel's CD-ROM subsystem.
The technical root cause of this vulnerability lies in the improper casting of an unsigned long value to an int type during the cdrom_ioctl_select_disc function execution. This casting operation creates a scenario where the bounds checking mechanism fails to properly validate input parameters, allowing malicious code to bypass intended security boundaries. When a local attacker submits crafted input to the ioctl interface, the unsigned long value gets truncated or sign-extended during the conversion to int, which can result in negative values being interpreted as valid indices. This type conversion issue creates a condition where kernel memory can be accessed beyond the intended boundaries, effectively leaking kernel memory contents to unprivileged userspace processes.
The operational impact of this vulnerability is significant for systems running affected Linux kernel versions, as it enables local privilege escalation through information disclosure. Attackers can exploit this flaw to extract sensitive kernel data such as stack contents, heap data, or other kernel memory structures that may contain credentials, cryptographic keys, or system configuration information. The vulnerability is particularly concerning because it requires no special privileges beyond normal user access, making it an attractive target for attackers seeking to gather intelligence about the target system. The similarity to CVE-2018-10940 and CVE-2018-16658 indicates this represents a broader class of type conversion vulnerabilities affecting kernel subsystems that handle ioctl operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-128, which addresses "Wrap or Overflow" conditions in integer operations, and demonstrates the critical importance of proper type handling in kernel space programming. The flaw also corresponds to ATT&CK technique T1059.001, "Command and Scripting Interpreter: PowerShell" and T1068, "Exploitation for Privilege Escalation," as it provides a mechanism for local attackers to escalate privileges through memory disclosure. The vulnerability's exploitation potential is heightened by the fact that it affects core kernel components that are frequently accessed, making it a persistent threat vector across various system configurations. Organizations should prioritize patching this vulnerability through kernel updates, as the information leak could potentially expose sensitive system data that could be leveraged for more sophisticated attacks. The vulnerability underscores the necessity of rigorous code review processes for kernel-level operations and proper bounds checking implementations to prevent similar issues in other subsystems.