CVE-2018-13098 in Linux
Summary
by MITRE
An issue was discovered in fs/f2fs/inode.c in the Linux kernel through 4.17.3. A denial of service (slab out-of-bounds read and BUG) can occur for a modified f2fs filesystem image in which FI_EXTRA_ATTR is set in an inode.
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Analysis
by VulDB Data Team • 03/29/2023
The vulnerability identified as CVE-2018-13098 represents a critical flaw in the Linux kernel's f2fs (Flash-Friendly File System) implementation that manifests through improper handling of filesystem metadata. This issue exists within the fs/f2fs/inode.c source file and affects Linux kernel versions up to 4.17.3, creating a scenario where maliciously crafted filesystem images can trigger system instability. The vulnerability specifically targets the handling of file attributes when the FI_EXTRA_ATTR flag is present in inode structures, exposing the kernel to potential exploitation through crafted filesystem modifications.
The technical nature of this vulnerability stems from a slab out-of-bounds read condition that occurs when the kernel processes filesystem images with modified metadata. When FI_EXTRA_ATTR is set in an inode, the kernel's processing logic fails to properly validate the bounds of memory access operations, leading to reading data beyond the allocated memory slab boundaries. This memory corruption scenario ultimately results in a kernel BUG condition that terminates the system's ability to continue normal operations. The flaw operates at the kernel level where memory management and filesystem parsing intersect, making it particularly dangerous as it can be triggered through legitimate filesystem access operations.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attack vectors. While the primary effect manifests as a system crash or reboot, the underlying memory corruption could theoretically be exploited to escalate privileges or execute arbitrary code within kernel space. Attackers could craft malicious filesystem images that, when mounted, would trigger the out-of-bounds read condition and cause the kernel to panic. This vulnerability affects systems that utilize f2fs filesystems, particularly those running Linux kernel versions within the affected range, making it a significant concern for embedded systems, servers, and devices that rely on flash storage technologies.
Security mitigations for CVE-2018-13098 primarily involve upgrading to kernel versions that contain the appropriate patches, specifically those beyond version 4.17.3 where the vulnerability has been addressed. System administrators should prioritize kernel updates across all affected systems, particularly those that mount f2fs filesystems or could be exposed to untrusted filesystem images. Additionally, implementing proper filesystem validation procedures and restricting access to filesystem images from untrusted sources can help reduce the attack surface. Organizations should also consider monitoring for suspicious filesystem mounting operations and implementing automated patch management processes to ensure timely remediation of this and similar kernel-level vulnerabilities.
This vulnerability aligns with CWE-125: Out-of-bounds Read, which classifies memory access violations that occur when programs read beyond allocated memory boundaries. The issue also relates to ATT&CK technique T1068: Exploitation for Privilege Escalation, as kernel-level memory corruption can potentially enable attackers to gain elevated system privileges. The f2fs filesystem implementation represents a specialized storage subsystem that requires careful validation of input data, and this vulnerability demonstrates the importance of robust bounds checking in kernel code. The flaw's classification as a kernel-level vulnerability emphasizes the need for comprehensive security testing of storage subsystems and proper input validation mechanisms in operating system components.