CVE-2026-89610
Summary
by MITRE • 09/11/2026
In the Linux kernel, the following vulnerability has been resolved:
ntfs: verify run length exceeding volume boundary
The mapping pairs decoder validates that the starting LCN is within the volume but does not check if the run extends beyond the volume boundary.
A malformed NTFS image with a crafted mapping pairs array could cause the kernel to access memory beyond the volume boundary, potentially leading to memory corruption and privilege escalation.
Add validation to ensure lcn + length stays within nr_clusters.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in the Linux kernel's New Technology File System driver involves an insufficient input validation mechanism during the parsing of NTFS mapping pairs arrays. The ntfs file system implementation relies on a mapping pairs decoder to translate logical cluster numbers into physical location numbers, which is critical for locating data extents on disk storage media. While the existing code correctly validates that the starting Logical Cluster Number falls within the defined volume boundaries, it fails to perform a subsequent check ensuring that the entire run of clusters described by the entry remains within those same limits. This oversight creates a scenario where a crafted or malformed NTFS image can specify a cluster range that begins inside the valid volume space but extends significantly beyond its end boundary.
From a technical perspective, this flaw constitutes an out-of-bounds read and potentially write operation depending on how the kernel utilizes the retrieved data structures. When the decoder processes such a maliciously constructed mapping pair, it calculates memory addresses or disk offsets based on the unvalidated length field combined with the starting cluster number. Since the upper bound of the volume is not checked against the sum of these two values, the kernel may attempt to access metadata or file system structures that reside outside the allocated and protected regions associated with the specific NTFS volume. This lack of boundary enforcement allows an attacker who can supply a malicious disk image or mountable storage device to trigger memory corruption within the kernel space.
The operational impact of this vulnerability is severe, primarily due to its potential for privilege escalation. By exploiting the out-of-bounds access, an unprivileged local user could corrupt critical kernel data structures, leading to arbitrary code execution with root privileges. This aligns directly with CWE-125 Out-of-bounds Read and CWE-787 Out-of-bounds Write in the Common Weakness Enumeration taxonomy, as the core issue is the failure to validate array bounds before accessing memory locations derived from user-controlled input. Furthermore, this exploitation vector relates to ATT&CK technique T1068 Exploitation for Privilege Escalation, where attackers leverage software vulnerabilities to gain higher-level access on a compromised system. The risk is particularly acute in environments where users are permitted to mount external storage devices or virtual disk images without strict administrative oversight.
To mitigate this vulnerability, the Linux kernel maintainers have implemented a validation check that ensures the calculated end of the cluster run does not exceed the total number of clusters available in the volume. This fix involves verifying that the sum of the starting Logical Cluster Number and the length of the run remains less than or equal to nr_clusters, which represents the total capacity of the file system volume. System administrators should ensure their systems are updated with the latest kernel patches containing this specific correction. Additionally, organizations should enforce strict policies regarding the mounting of external storage devices and implement integrity checks on disk images before they are attached to production environments to prevent the introduction of malformed file system structures that could trigger such parsing errors.