CVE-2026-99156 scsi: st: Fix use-after-free race between st_remove() and st_open()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99156?
CVE-2026-99156 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
scsi: st: Fix use-after-free race between st_remove() and st_open()
st_remove() drops the probe reference on the scsi_tape with kref_put() and only afterwards removes its index from st_index_idr. If that was the last reference, scsi_tape_release() frees the structure while it is still published in the idr.
scsi_tape_get(), called from st_open(), looks up the tape in st_index_idr and takes a reference under st_ref_mutex and st_index_lock. remove_cdevs() does not wait for opens that are already past chrdev_open(), so an open that is blocked on st_ref_mutex while st_remove() holds it can take the mutex as soon as st_remove() drops it, find the freed tpnt in the idr and call kref_get() on it:
BUG: KASAN: slab-use-after-free in st_open Write of size 4 ... st_open (drivers/scsi/st.c:254 drivers/scsi/st.c:1291) chrdev_open ... Freed by task ...: kfree st_remove (drivers/scsi/st.c:4512)
Remove the index from the idr before dropping the reference, all under st_ref_mutex. A concurrent scsi_tape_get() now either runs first and holds a valid reference that keeps the tape alive, or runs afterwards and finds nothing, so st_open() fails with -ENXIO.
This restores the ordering st_remove() had before the conversion to st_index_idr, where the tape was unpublished from scsi_tapes[] before the final kref_put().
Which versions are affected by CVE-2026-99156?
How do I fix CVE-2026-99156?
Upgrade to a fixed version.
Is CVE-2026-99156 being exploited?
There is no known exploitation of CVE-2026-99156 in the wild and no public exploit code.
Sources
Also known as AZL-111296, BELL-CVE-2026-99156, DEBIAN-CVE-2026-99156, GHSA-3wp3-5585-mc8q, UBUNTU-CVE-2026-99156.