DEBIAN-CVE-2026-89614

In the Linux kernel, the following vulnerability has been resolved:  ntfs: bound the free-cluster bitmap scan to the volume  vol->lcnemptybitsperpage is sized from vol->nrclusters at mount, but ntfsclusteralloc() bounds its scan of that array by the size of $Bitmap. Those are independent on-disk quantities and the mount-time check only rejects a $Bitmap that is too small, so an image whose $Bitmap covers more clusters than the volume has lets the scan index past the array.  A run whose LCN lies in that gap takes the allocator straight there, since the caller passes the file's own last LCN as its locality hint.  KASAN reports a slab out-of-bounds read when a file on such a volume is extended.  Clamp the scan to what that array covers, mirroring the maxindex calculation the mount-time scan already uses, and reject a decoded LCN at or beyond nr_clusters in the mapping pairs decoder.  Conforming volumes are unaffected.