CVE-2026-90199 fs/ntfs3: reject out-of-range evcn in mi_enum_attr()

Q: Is CVE-2026-90199 being exploited?

There is no known exploitation of CVE-2026-90199 in the wild and no public exploit code.

High 7.8 Published 17 Sep 2026 Updated 19 Oct 2026

A malformed NTFS3 disk image can trigger an integer overflow in the kernel, leading to a denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2026-90199?

CVE-2026-90199 is a high-severity vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: reject out-of-range evcn in mi_enum_attr()

In mi_enum_attr(), the start/end VCN validation for non-resident attributes is:

if (svcn > evcn + 1) goto out;

When evcn is U64_MAX the "evcn + 1" expression wraps to 0 and any svcn passes the check. For evcn values close to U64_MAX (but not equal to it) the right-hand side is still a meaningless near-wrap upper bound, so a malformed on-disk attribute with svcn == 0 and evcn near U64_MAX can pass mi_enum_attr() unrejected.

VCN (virtual cluster number) is a cluster index, so any valid evcn is bounded by the volume's total cluster count, which ntfs3 holds in sbi->used.bitmap.nbits (set up in ntfs_init_from_boot() before any caller of mi_enum_attr() runs). Reject evcn values that fall outside this range.

However, an empty non-resident attribute (no allocated clusters) is legitimately encoded with svcn == 0 and evcn == -1 (U64_MAX), e.g. via attr->nres.evcn = cpu_to_le64((u64)vcn - 1) with vcn == 0. That sentinel must keep passing, so exclude evcn == U64_MAX from the range check. The existing "svcn > evcn + 1" test still tolerates the sentinel ("0 > 0" is false) and continues to require svcn == 0 for it, while the range check rejects every other out-of-range evcn and thereby also defuses the "evcn + 1" wraparound.

svcn does not need its own bound: once evcn < nbits, "svcn > evcn + 1" implies svcn <= nbits.

[[email protected]: fixed evcn check]

Which versions are affected by CVE-2026-90199?

How do I fix CVE-2026-90199?

Apply the vendor's patch.

Is CVE-2026-90199 being exploited?