CVE-2026-90117 ntfs: validate usa_ofs before preserving the update sequence number
A use-after-free vulnerability in the Linux kernel NTFS driver allows local attackers to cause a system crash or potentially execute code via a crafted filesystem image.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90117?
CVE-2026-90117 is an use after free vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ntfs: validate usa_ofs before preserving the update sequence number
When ntfs_mft_record_alloc() reuses a free mft record it reads the old update sequence number straight from the on-disk record:
usn = *(__le16 *)((u8 *)m + le16_to_cpu(m->usa_ofs));
Here m points into the raw $MFT page-cache folio, which still holds unvalidated, MST-protected bytes: the folio is read by a plain iomap_read_folio() and neither post_read_mst_fixup() nor ntfs_mft_record_check() has run on it (both work on private copies). m->usa_ofs is therefore an untrusted u16, and a corrupted record can put it past the end of the record so the two-byte read lands outside the folio. Reading such a record while creating a file gives, under KASAN:
BUG: KASAN: use-after-free in ntfs_mft_record_alloc+... Read of size 2 at addr ... ntfs_mft_record_alloc -> __ntfs_create -> ntfs_create -> path_openat
Only preserve the old update sequence number when usa_ofs is even and in range, mirroring the check ntfs_mft_record_check() already applies; otherwise leave usn zero, which the existing restore below skips.
Which versions are affected by CVE-2026-90117?
How do I fix CVE-2026-90117?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-90117 being exploited?
There is no known exploitation of CVE-2026-90117 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90117, GHSA-v5jv-j5cw-ggjq, UBUNTU-CVE-2026-90117.