CVE-2018-10323 in Linux
Summary
by MITRE
The xfs_bmap_extents_to_btree function in fs/xfs/libxfs/xfs_bmap.c in the Linux kernel through 4.16.3 allows local users to cause a denial of service (xfs_bmapi_write NULL pointer dereference) via a crafted xfs image.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2018-10323 resides within the Linux kernel's XFS filesystem implementation, specifically in the xfs_bmap_extents_to_btree function located in fs/xfs/libxfs/xfs_bmap.c. This flaw represents a critical denial of service vulnerability that can be exploited by local attackers through the manipulation of crafted XFS image files. The vulnerability manifests as a NULL pointer dereference during the xfs_bmapi_write operation, which occurs when the kernel attempts to process extended attribute mappings within the XFS filesystem structure. The issue stems from inadequate input validation and error handling within the bmap (bitmap) subsystem that manages extent allocation and conversion processes in XFS filesystems.
The technical exploitation of this vulnerability involves constructing a malformed XFS image file that triggers the specific code path where the xfs_bmap_extents_to_btree function fails to properly initialize or validate pointers before dereferencing them. This condition typically occurs when the kernel processes certain combinations of extent mappings that lead to an inconsistent state in the bmap data structures. The vulnerability is classified under CWE-476 as a NULL pointer dereference, which represents a common class of software defects where a program attempts to access memory through a pointer that has not been properly initialized or has been set to NULL. The flaw demonstrates a failure in the kernel's memory management and validation routines that should have prevented the execution of invalid memory access patterns.
From an operational impact perspective, this vulnerability allows local attackers to trigger a system-wide denial of service condition that can render the affected system unstable or completely unresponsive. The NULL pointer dereference causes the kernel to generate a segmentation fault or page fault, which typically results in the immediate termination of the process attempting to access the invalid memory location. In the context of XFS filesystems, this can lead to complete filesystem unavailability, requiring system reboot or manual intervention to restore normal operations. The vulnerability affects all Linux kernel versions through 4.16.3, making it particularly concerning for systems that rely on XFS for storage management. The impact extends beyond simple service disruption as the kernel crash can potentially corrupt filesystem metadata or cause data loss if the system does not properly handle the kernel panic conditions.
The mitigation strategies for CVE-2018-10323 primarily involve applying the official kernel patches released by the Linux kernel security team, which address the root cause by implementing proper pointer validation and error handling within the xfs_bmap_extents_to_btree function. System administrators should prioritize updating their kernel versions to 4.16.4 or later, which contain the necessary fixes to prevent the NULL pointer dereference condition. Additionally, implementing runtime monitoring and intrusion detection systems can help identify potential exploitation attempts through unusual filesystem access patterns or memory allocation behaviors. Organizations should also consider implementing filesystem-level access controls and monitoring to detect unauthorized manipulation of XFS image files. The vulnerability aligns with ATT&CK technique T1059.007 for execution through kernel modules and T1499.004 for endpoint denial of service, making it relevant to both defensive and offensive cybersecurity operations. Regular kernel security auditing and vulnerability assessment procedures should include checks for similar patterns in other filesystem implementations to prevent analogous issues in related subsystems.