---
id: "CVE-2026-99156"
kind: "vulnerability"
aliases: ["CVE-2026-99156"]
title: "Linux kernel SCSI tape driver: use-after-free when opening a removed tape"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["linux-kernel", "runtime", "scsi-tape"]
not_affected_if: ["no-scsi-tape-drive"]
published_at: "2026-10-28T11:17:35+00:00"
first_seen_at: "2026-10-28T11:32:36+00:00"
updated_at: "2026-10-28T11:35:49+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99156", "first_seen_at": "2026-10-28T11:32:36+00:00"}]
---

# Linux kernel SCSI tape driver: use-after-free when opening a removed tape

In the Linux kernel SCSI tape driver (st), a race between device removal and opening lets a process open a tape device whose structure was already freed. The sources describe this as a use-after-free, which can corrupt memory; the sources do not state a privilege or impact level.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Install a Linux kernel release that includes the upstream commit 'scsi: st: Fix use-after-free race between st_remove() and st_open()'; the sources do not name a version.

## Timeline

- 2026-10-28T11:32:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99156

## From the sources

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().

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