CVE-2018-14614 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel through 4.17.10. There is an out-of-bounds access in __remove_dirty_segment() in fs/f2fs/segment.c when mounting an f2fs image.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2018-14614 represents a critical out-of-bounds memory access flaw within the Linux kernel's F2FS (Flash-Friendly File System) implementation. This issue affects kernel versions through 4.17.10 and manifests during the mounting process of F2FS filesystem images. The flaw exists in the __remove_dirty_segment() function located in the fs/f2fs/segment.c source file, making it particularly dangerous as it occurs during filesystem initialization when the kernel attempts to manage dirty segments within the flash storage subsystem.
The technical nature of this vulnerability stems from improper bounds checking within the segment management logic of the F2FS filesystem driver. When an F2FS image is mounted, the kernel's segment management code attempts to remove dirty segments from memory structures without adequate validation of array indices or segment boundaries. This allows an attacker who can control the F2FS image content to potentially trigger memory corruption through carefully crafted filesystem structures. The out-of-bounds access can result in arbitrary code execution within kernel space, as the attacker can manipulate memory locations beyond the intended segment array boundaries. This type of vulnerability falls under CWE-129, which specifically addresses insufficient bounds checking, and represents a classic buffer overflow scenario that can be exploited to gain elevated privileges.
The operational impact of CVE-2018-14614 extends beyond simple system crashes or denial of service conditions. Since this vulnerability occurs during filesystem mounting, it can be exploited through various attack vectors including malicious USB drives, network file shares, or any mechanism that allows untrusted F2FS images to be mounted. The exploitation potential is particularly concerning because F2FS is commonly used on mobile devices, embedded systems, and storage devices where automatic mounting of removable media is enabled by default. This vulnerability directly aligns with ATT&CK technique T1059.005, which involves executing malicious code through kernel-level exploits, and can be leveraged to establish persistent backdoors or escalate privileges from unprivileged users to root access. The attack surface is broad as any system running a vulnerable kernel version and mounting F2FS filesystems is potentially at risk.
Mitigation strategies for CVE-2018-14614 primarily involve immediate kernel updates to versions 4.17.11 or later where the fix has been implemented. The patch addresses the issue by adding proper bounds checking to ensure that segment indices remain within valid array boundaries before any memory access operations occur. System administrators should also implement additional protective measures such as disabling automatic mounting of removable media, particularly F2FS filesystems, and ensuring that only trusted filesystem images are mounted on production systems. Organizations should conduct comprehensive vulnerability assessments to identify systems running vulnerable kernel versions and prioritize patching efforts accordingly. The fix demonstrates proper defensive programming practices that align with secure coding guidelines, specifically addressing the root cause through input validation rather than attempting to recover from the error after it occurs. Network segmentation and access controls should be enhanced to limit potential exploitation of this vulnerability through remote attack vectors, as the issue can be triggered through various file transfer mechanisms that result in automatic mounting of F2FS images.