CVE-2018-13100 in Linux
Summary
by MITRE
An issue was discovered in fs/f2fs/super.c in the Linux kernel through 4.17.3, which does not properly validate secs_per_zone in a corrupted f2fs image, as demonstrated by a divide-by-zero error.
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Analysis
by VulDB Data Team • 04/03/2023
The vulnerability identified as CVE-2018-13100 resides within the Linux kernel's f2fs file system implementation, specifically in the fs/f2fs/super.c component. This flaw represents a critical validation failure that occurs when processing corrupted f2fs image files, potentially leading to system instability and denial of service conditions. The issue manifests when the kernel attempts to handle file system images that have been deliberately or accidentally corrupted, particularly focusing on the secs_per_zone parameter which defines the number of sectors per zone within the f2fs structure. This parameter validation gap creates a scenario where malicious actors or system errors could trigger unexpected behavior in the kernel's file system handling routines.
The technical exploitation of this vulnerability occurs through a divide-by-zero error condition that arises when the kernel processes corrupted f2fs images containing invalid secs_per_zone values. This type of error represents a classic validation flaw that falls under CWE-369, which specifically addresses the division by zero condition in software implementations. When the kernel attempts to perform arithmetic operations using the invalid secs_per_zone value, particularly in calculations related to zone management and sector allocation, the system encounters a division operation with a zero denominator, causing immediate system termination or kernel panic. The vulnerability is particularly concerning because it operates at the kernel level where such errors can result in complete system crashes without proper recovery mechanisms.
The operational impact of CVE-2018-13100 extends beyond simple system crashes to encompass broader security implications within Linux environments that utilize the f2fs file system. Systems running Linux kernel versions through 4.17.3 are susceptible to this vulnerability, making it a significant concern for enterprise environments where f2fs is deployed for storage solutions. The vulnerability can be exploited through various attack vectors including malicious file system images, corrupted storage media, or through manipulation of file system metadata that would be processed during normal system operations. This flaw can be categorized under ATT&CK technique T1499.001 which covers File System Wipe, as the divide-by-zero error can effectively render the file system inaccessible and cause complete system failure. The vulnerability particularly affects systems using f2fs for root file systems, journaling, or storage solutions where the kernel must process potentially corrupted file system structures during boot or operation.
Mitigation strategies for CVE-2018-13100 primarily involve updating to patched kernel versions where the validation logic for secs_per_zone has been properly implemented. System administrators should prioritize kernel updates to versions that include the specific fix for this validation flaw, typically found in kernel releases following version 4.17.3. Additionally, implementing proper file system integrity monitoring and regular validation procedures can help detect corrupted f2fs images before they are processed by the kernel. The fix involves adding proper bounds checking and validation logic for the secs_per_zone parameter before any arithmetic operations are performed, ensuring that zero values are rejected or handled gracefully. Organizations should also consider implementing network segmentation and access controls to limit exposure of systems running vulnerable kernel versions, particularly in environments where f2fs file systems are deployed. The vulnerability demonstrates the critical importance of proper input validation in kernel space operations and the potential for seemingly minor validation gaps to result in catastrophic system failures.