CVE-2018-13097 in Linux
Summary
by MITRE
An issue was discovered in fs/f2fs/super.c in the Linux kernel through 4.17.3. There is an out-of-bounds read or a divide-by-zero error for an incorrect user_block_count in a corrupted f2fs image, leading to a denial of service (BUG).
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Analysis
by VulDB Data Team • 03/29/2023
The vulnerability identified as CVE-2018-13097 represents a critical flaw in the Linux kernel's f2fs filesystem implementation that affects versions through 4.17.3. This issue resides within the fs/f2fs/super.c file and demonstrates a classic case of insufficient input validation that can lead to system instability and denial of service conditions. The vulnerability specifically manifests when processing corrupted f2fs images where the user_block_count parameter contains incorrect values, creating a scenario where the kernel's filesystem driver fails to properly handle malformed data structures.
The technical nature of this vulnerability stems from an out-of-bounds read condition or potential divide-by-zero error that occurs when the f2fs superblock parsing code encounters an invalid user_block_count value in corrupted filesystem images. This flaw operates at the kernel level where the filesystem driver attempts to process filesystem metadata without adequate validation of the block count parameter. When the user_block_count field contains unexpected values, the kernel's processing logic can either attempt to access memory beyond valid bounds or perform division operations with zero, both of which can trigger kernel panics or system crashes.
From an operational impact perspective, this vulnerability creates significant denial of service conditions for systems running affected Linux kernels with f2fs filesystems. The out-of-bounds read or divide-by-zero error can cause the entire kernel to crash or enter an unrecoverable state, effectively rendering the affected system unusable until reboot occurs. This type of vulnerability is particularly concerning in production environments where filesystem stability is critical, as it can be triggered by simply mounting a corrupted f2fs image, making it exploitable through various attack vectors including malicious media insertion or compromised storage devices.
The vulnerability aligns with CWE-129: Improper Validation of Array Index and CWE-369: Divide by Zero, both of which are fundamental security weaknesses that demonstrate poor input validation practices in kernel code. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain under the T1499.004 technique for network denial of service, or potentially as a component in privilege escalation scenarios where an attacker could leverage kernel instability for further exploitation. The flaw represents a classic example of how filesystem corruption handling can lead to kernel-level vulnerabilities, emphasizing the importance of robust error handling in kernel space code.
Mitigation strategies for this vulnerability primarily involve upgrading to kernel versions where the issue has been patched, specifically those beyond version 4.17.3. System administrators should implement comprehensive patch management processes to ensure all affected systems receive updates promptly. Additionally, monitoring for unusual filesystem corruption patterns and implementing proper filesystem integrity checks can help detect potential exploitation attempts. Organizations should also consider implementing filesystem-specific security measures such as read-only mounting of potentially untrusted filesystems and regular filesystem validation routines to minimize exposure to this class of vulnerability.