# CVE-2026-43054: scsi: target: tcm_loop: Drain commands in target_reset handler

> A missing command drain in the tcm_loop reset handler causes a resource leak, hanging LUN unlink operations and leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-43054, DEBIAN-CVE-2026-43054, GHSA-mf6r-pgpm-mqvq, ROOT-OS-UBUNTU-2204-CVE-2026-43054, ROOT-OS-UBUNTU-2404-CVE-2026-43054, UBUNTU-CVE-2026-43054

## What is CVE-2026-43054?

CVE-2026-43054 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 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:

scsi: target: tcm_loop: Drain commands in target_reset handler

tcm_loop_target_reset() violates the SCSI EH contract: it returns SUCCESS
without draining any in-flight commands.  The SCSI EH documentation
(scsi_eh.rst) requires that when a reset handler returns SUCCESS the driver
has made lower layers "forget about timed out scmds" and is ready for new
commands.  Every other SCSI LLD (virtio_scsi, mpt3sas, ipr, scsi_debug,
mpi3mr) enforces this by draining or completing outstanding commands before
returning SUCCESS.

Because tcm_loop_target_reset() doesn't drain, the SCSI EH reuses in-flight
scsi_cmnd structures for recovery commands (e.g. TUR) while the target core
still has async completion work queued for the old se_cmd.  The memset in
queuecommand zeroes se_lun and lun_ref_active, causing
transport_lun_remove_cmd() to skip its percpu_ref_put().  The leaked LUN
reference prevents transport_clear_lun_ref() from completing, hanging
configfs LUN unlink forever in D-state:

  INFO: task rm:264 blocked for more than 122 seconds.
  rm              D    0   264    258 0x00004000
  Call Trace:
   __schedule+0x3d0/0x8e0
   schedule+0x36/0xf0
   transport_clear_lun_ref+0x78/0x90 [target_core_mod]
   core_tpg_remove_lun+0x28/0xb0 [target_core_mod]
   target_fabric_port_unlink+0x50/0x60 [target_core_mod]
   configfs_unlink+0x156/0x1f0 [configfs]
   vfs_unlink+0x109/0x290
   do_unlinkat+0x1d5/0x2d0

Fix this by making tcm_loop_target_reset() actually drain commands:

 1. Issue TMR_LUN_RESET via tcm_loop_issue_tmr() to drain all commands that
    the target core knows about (those not yet CMD_T_COMPLETE).

 2. Use blk_mq_tagset_busy_iter() to iterate all started requests and
    flush_work() on each se_cmd — this drains any deferred completion work
    for commands that already had CMD_T_COMPLETE set before the TMR (which
    the TMR skips via __target_check_io_state()).  This is the same pattern
    used by mpi3mr, scsi_debug, and libsas to drain outstanding commands
    during reset.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime)

## Which versions are affected by CVE-2026-43054?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43054?

Apply the vendor's patch.

## Is CVE-2026-43054 being exploited?

There is no known exploitation of CVE-2026-43054 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43054 and fix it if it is affected.

What it is: CVE-2026-43054 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43054 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43054/ (Markdown: https://insights.sbomify.com/CVE-2026-43054/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43054
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43054
- OSV: https://osv.dev/vulnerability/CVE-2026-43054

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43054/
Summaries are generated and may contain mistakes; the official description above is the record.