CVE-2026-98138 in Linux
Summary
by MITRE • 09/25/2026
In the Linux kernel, the following vulnerability has been resolved:
ntfs: do not mark the volume clean in sync_fs when errors were recorded
ntfs_put_super() and the remount-read-only path both clear the dirty bit only when NVolErrors(vol) is false. ntfs_sync_fs() clears it unconditionally, so any sync() on a volume that recorded an error marks that volume clean. A volume without this set is then seen as not needing recovery and it does not run one, so whatever went wrong is never repaired.
This change skips resetting the dirty bit when there are volume errors.
Reproduced on a volume whose $MFTMirr does not match $MFT, which sets the error flag while leaving the mount read-write: after a write and a sync, the on-disk volume flags read 0x0000 with this driver and 0x0001 with the guard in place.
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Analysis
by VulDB Data Team • 09/25/2026
The vulnerability identified within the Linux kernel's NTFS filesystem driver involves an incorrect handling of volume state during file system synchronization operations, specifically within the ntfs_sync_fs function. This issue stems from a logical inconsistency where the dirty bit is cleared unconditionally regardless of whether critical errors have been recorded on the volume. In standard operating systems like Windows and in correct Linux implementations such as ext4 or xfs, the clean flag indicates that the file system metadata is consistent with its journal or log. When inconsistencies are detected, the volume must be marked as dirty to ensure that a recovery process runs at the next mount attempt. The flaw here allows an administrator or application to perform write operations and subsequently sync those changes while ignoring underlying corruption indicators, effectively masking the presence of errors from subsequent checks.
The technical root cause lies in the divergence between how different paths handle volume state transitions. Functions such as ntfs_put_super and the remount-read-only path correctly check for NVolErrors before clearing the dirty bit, ensuring that volumes with known issues remain marked for recovery. However, ntfs_sync_fs bypasses this safety check by resetting the clean flag unconditionally. This creates a scenario where an administrator might attempt to repair or investigate a corrupted volume but inadvertently clears the error state through routine synchronization calls. Consequently, when the system is rebooted or the file system is remounted, it perceives itself as healthy and skips necessary consistency checks like chkdsk equivalents in Linux environments.
The operational impact of this vulnerability is significant for data integrity and system reliability. By allowing a corrupted volume to be marked clean after synchronization, the driver prevents automatic recovery mechanisms from triggering upon subsequent mounts. This means that structural inconsistencies, such as mismatches between critical metadata structures like $MFTMirr and $MFT, remain unaddressed on disk. Over time, this can lead to silent data corruption, where files appear accessible but contain invalid pointers or lost clusters because the file system engine believes no repair is needed. In severe cases, continued use of a volume in this state could exacerbate structural damage, potentially leading to complete file system failure and loss of access to stored data.
This flaw aligns with CWE-253 Incorrect Check of Condition, as the code fails to verify the error status before modifying the volume's clean flag. It also relates to CWE-754 Improper Check for Unusual or Exceptional Conditions because it does not handle the exceptional state of a corrupted file system appropriately during routine maintenance operations like syncing. From an ATT&CK perspective, while this is primarily a reliability issue rather than a direct exploitation vector for privilege escalation, it can be leveraged in scenarios involving persistence or evasion if an attacker seeks to hide evidence of tampering by ensuring that forensic tools do not flag the volume as corrupted upon inspection after a sync operation.
Mitigation strategies involve applying kernel patches that update ntfs_sync_fs to respect the NVolErrors flag before clearing the dirty bit, mirroring the logic already present in other cleanup paths within the driver. System administrators should ensure their kernels are updated with these fixes and regularly verify file system integrity using tools like fsck.ntfs or similar utilities provided by the distribution. Additionally, monitoring logs for NTFS-related errors can help detect volumes that have entered an inconsistent state before they are inadvertently marked clean through synchronization operations. Regular backups remain essential as a final safeguard against data loss resulting from such logical flaws in storage drivers.