# CVE-2026-80589: block: stop the timeout timer when releasing a never added disk

> A use-after-free vulnerability in the Linux kernel block layer allows attackers to cause a system crash or potentially execute code via a race condition during disk release.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97694, BELL-CVE-2026-80589, DEBIAN-CVE-2026-80589, GHSA-rf5w-wp84-mh25, UBUNTU-CVE-2026-80589

## What is CVE-2026-80589?

CVE-2026-80589 is a critical use after free vulnerability in Linux, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

block: stop the timeout timer when releasing a never added disk

disk_release() undoes blk_mq_init_allocated_queue() for a disk whose
probe failed before add_disk(), but it only calls blk_mq_exit_queue().
Nothing there stops q->timeout, and that timer rolls forward: it stays
pending until it next expires, not until the last request completes.
So if the driver issued any I/O before adding the disk, the
request_queue is freed while still linked into a timer wheel bucket.

Commit 6f8191fdf41d ("block: simplify disk shutdown") dropped the
blk_cleanup_queue() call that used to stop it.  __del_gendisk() and
blk_mq_destroy_queue() still do; only the probe failure path lost it.

nvme gets there because nvme_update_ns_info() submits Report Zones or
FDP io-mgmt-recv on ns->queue before the disk is added, so a later
failure - a concurrent reset setting NVME_CTRL_FROZEN, or
device_add_disk() failing - lands in put_disk() with the timer armed:

  BUG: KASAN: slab-use-after-free in detach_if_pending+0x30c/0x340
  Write of size 8 at addr ffff888004d71310 by task kworker/u8:2/37
   __timer_delete_sync+0x156/0x240 kernel/time/timer.c:1621
   blk_sync_queue+0x22/0x40 block/blk-core.c:222
   nvme_sync_queues+0x100/0x150 drivers/nvme/host/core.c:5362
   nvme_reset_work+0x138/0x930 drivers/nvme/host/pci.c:3264

  Allocated by task 34:
   __blk_mq_alloc_disk+0x33/0x100 block/blk-mq.c:4462
   nvme_alloc_ns+0x290/0x3870 drivers/nvme/host/core.c:4146

  Freed by task 0:
   blk_free_queue_rcu+0x3a/0x50 block/blk-core.c:254
   rcu_core+0xc10/0x1730 kernel/rcu/tree.c:2857

The queue being synced there is ctrl->admin_q, only a victim sharing a
timer wheel bucket with the freed queue's dangling entry; other runs
tripped in enqueue_timer(), __run_timers() or blk_mq_timeout_work().
Failing nvme_alloc_ns() with a debug patch makes it deterministic: one
leaked timer trips KASAN within seconds, while 1987 patched releases
produced no splat.

Stop the timer and the queue work items before blk_mq_exit_queue(), like
blk_mq_destroy_queue() does.

Found by FuzzNvme.

## Which versions are affected by CVE-2026-80589?


## How do I fix CVE-2026-80589?

Apply the vendor's patch.

## Is CVE-2026-80589 being exploited?

There is no known exploitation of CVE-2026-80589 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80589 and fix it if it is affected.

What it is: CVE-2026-80589 is a critical use after free vulnerability in Linux, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-80589 in the wild and no public exploit code.

Affected product: Linux. 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-2026-80589/ (Markdown: https://insights.sbomify.com/CVE-2026-80589/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80589
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80589
- OSV: https://osv.dev/vulnerability/CVE-2026-80589

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80589/
Summaries are generated and may contain mistakes; the official description above is the record.