# CVE-2026-99108: ntfs: fix FITRIM range alignment

- Also known as: EUVD-2026-112008
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-10-28 · Updated: 2026-10-28

## Summary

The Linux kernel's NTFS filesystem driver (ntfs) is affected when using the FITRIM discard operation on volumes whose free space is not aligned to the device's discard granularity. In this case, the trim could extend beyond free space into allocated data, potentially causing data loss by discarding in-use blocks.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 7.1

## Description

In the Linux kernel, the following vulnerability has been resolved: ntfs: fix FITRIM range alignment ntfs_trim_fs() aligns the start of a free extent up to the device discard granularity, but derives the discard length by aligning the original extent length down. When the free extent start is not discard-aligned, adding that length to the aligned start can extend the discard past the free extent and into allocated clusters. For example, with 4 KiB clusters and 32 KiB discard granularity, the free extent [4 KiB, 36 KiB) becomes the discard range [32 KiB, 64 KiB), so 28 KiB beyond the free extent may be discarded. Align the absolute end of the free extent down and derive the length from the two aligned endpoints. Skip extents that contain no full discard unit. Reproduced with a 4 KiB-cluster NTFS filesystem on scsi_debug configured for 32 KiB discard granularity and read-zero-after-trim. Before this change, FITRIM zeroed seven allocated 4 KiB clusters following an unaligned 32 KiB hole. With this change, the same data remains intact across FITRIM and remount.

## What to do

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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5e87da8ba8d3d647d89c754912e45c1f1a3bfc2e
- https://git.kernel.org/stable/c/03c6ecc4b4b13a3901f207152451fdd2d82e40c4

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