CVE-2025-40068 in Linux
Summary
by MITRE • 10/28/2025
In the Linux kernel, the following vulnerability has been resolved:
fs: ntfs3: Fix integer overflow in run_unpack()
The MFT record relative to the file being opened contains its runlist, an array containing information about the file's location on the physical disk. Analysis of all Call Stack paths showed that the values of the runlist array, from which LCNs are calculated, are not validated before run_unpack function.
The run_unpack function decodes the compressed runlist data format from MFT attributes (for example, $DATA), converting them into a runs_tree structure, which describes the mapping of virtual clusters (VCN) to logical clusters (LCN). The NTFS3 subsystem also has a shortcut for deleting files from MFT records - in this case, the RUN_DEALLOCATE command is sent to the run_unpack input, and the function logic provides that all data transferred to the runlist about file or directory is deleted without creating a runs_tree structure.
Substituting the runlist in the $DATA attribute of the MFT record for an arbitrary file can lead either to access to arbitrary data on the disk bypassing access checks to them (since the inode access check occurs above) or to destruction of arbitrary data on the disk.
Add overflow check for addition operation.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
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Analysis
by VulDB Data Team • 02/15/2026
The vulnerability CVE-2025-40068 represents a critical integer overflow flaw within the NTFS3 file system implementation of the Linux kernel, specifically affecting the run_unpack() function. This issue resides in the file system's handling of Master File Table (MFT) records where file location data is stored in runlists that map virtual cluster numbers to logical cluster numbers. The vulnerability stems from inadequate validation of runlist array values before processing within the run_unpack function, creating a path for malicious manipulation of file metadata that could lead to severe security implications.
The technical flaw manifests when the run_unpack function processes compressed runlist data from MFT attributes, particularly the $DATA attribute, converting this data into a runs_tree structure that maps virtual clusters to logical clusters. The vulnerability becomes apparent when analyzing the Call Stack paths that lead to the function execution, as the system fails to validate input values from the runlist array before processing. This validation gap allows for manipulation of the runlist data that can result in either unauthorized data access or deliberate data destruction. The system includes a shortcut mechanism for file deletion through RUN_DEALLOCATE commands, which bypasses normal structure creation and directly processes the runlist data, amplifying the potential impact of this vulnerability.
The operational impact of this vulnerability extends beyond simple file system corruption, as it creates opportunities for privilege escalation and data compromise. An attacker who can manipulate MFT records containing runlist data could potentially access arbitrary disk data without proper access controls, effectively bypassing the inode access check that normally protects file system resources. Additionally, the vulnerability could enable attackers to destroy arbitrary data on the disk through controlled manipulation of the runlist information, potentially causing significant system instability or data loss. The vulnerability affects systems running Linux kernels with NTFS3 file system support, particularly those handling files with complex runlist structures or those that may be subject to malicious MFT record modification.
The fix for this vulnerability involves implementing proper overflow checks for addition operations within the run_unpack function, specifically addressing the integer overflow that occurs when processing runlist data. This mitigation aligns with CWE-190, which addresses integer overflow and underflow conditions, and follows established security practices for preventing arithmetic overflow vulnerabilities. The vulnerability was discovered through systematic analysis by the Linux Verification Center using SVACE tools, highlighting the importance of automated verification in identifying such subtle but critical security flaws in kernel code. Organizations should prioritize updating their Linux kernel versions to address this vulnerability, as it represents a significant risk to system security and data integrity in environments where NTFS3 file systems are actively used. The fix ensures that all arithmetic operations within the run_unpack function properly validate input ranges and prevent overflow conditions that could be exploited to manipulate file system structures.