CVE-2026-99108 ntfs: fix FITRIM range alignment
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99108?
CVE-2026-99108 is a vulnerability in Linux, published on 28 Oct 2026.
Official 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.
Which versions are affected by CVE-2026-99108?
How do I fix CVE-2026-99108?
Upgrade to a fixed version.
Is CVE-2026-99108 being exploited?
There is no known exploitation of CVE-2026-99108 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-99108, GHSA-8qcr-mmv6-jjc8, UBUNTU-CVE-2026-99108.