CVE-2018-14656 in Linux
Summary
by MITRE
A missing address check in the callers of the show_opcodes() in the Linux kernel allows an attacker to dump the kernel memory at an arbitrary kernel address into the dmesg log.
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Analysis
by VulDB Data Team • 05/23/2023
The vulnerability identified as CVE-2018-14656 represents a critical information disclosure flaw within the Linux kernel's debugging interface. This issue stems from insufficient validation mechanisms in the show_opcodes() function call chain, which is typically used for kernel debugging purposes. The vulnerability specifically affects the kernel's ability to properly validate memory addresses before allowing access to kernel memory contents through the dmesg logging facility.
The technical implementation of this flaw occurs within the kernel's debugging subsystem where the show_opcodes() function lacks proper address validation checks. When attackers can manipulate the function parameters or trigger the function through specific kernel interfaces, they can bypass normal memory access controls and dump arbitrary kernel memory addresses to the dmesg log output. This represents a classic case of insufficient input validation and access control enforcement, which aligns with CWE-20 - Improper Input Validation and CWE-284 - Improper Access Control. The vulnerability essentially allows unauthorized memory dumping through kernel debugging interfaces that should normally be restricted to privileged operations.
The operational impact of this vulnerability is severe as it enables attackers to extract sensitive kernel memory contents including potential credentials, cryptographic keys, kernel pointers, and other confidential information that could be used for further exploitation. The dumped information in the dmesg log can reveal kernel memory layout details, which are crucial for advanced exploitation techniques such as kernel address space layout randomization (ASLR) bypasses and privilege escalation attacks. This vulnerability essentially provides an information leak that can significantly aid attackers in understanding the target system's kernel structure and identifying potential attack vectors.
From a threat modeling perspective, this vulnerability demonstrates a failure in the kernel's security boundary enforcement mechanisms. The ATT&CK framework would categorize this as a privilege escalation technique through information gathering, specifically under T1082 - System Information Discovery and T1068 - Exploitation for Privilege Escalation. The vulnerability could be exploited by unprivileged users or processes to gain insights into kernel memory structures, potentially leading to more sophisticated attacks. Organizations should consider this vulnerability as part of a broader exploitation chain where initial information gathering leads to more targeted attacks.
Mitigation strategies for CVE-2018-14656 involve applying the appropriate kernel security patches released by the Linux kernel development team. System administrators should ensure their kernel versions are updated to include the fixes that properly validate memory addresses before allowing access to kernel debugging interfaces. Additionally, monitoring dmesg output for suspicious memory dumps and implementing proper access controls on kernel debugging interfaces can help detect potential exploitation attempts. The vulnerability highlights the importance of proper input validation in kernel space and demonstrates why robust access control mechanisms are essential for maintaining kernel security boundaries. Organizations should also consider implementing kernel memory protection mechanisms and regularly auditing kernel debugging interfaces for unauthorized access attempts.