# CVE-2026-90173: smb: smbdirect: free completion queues with ib_free_cq()

> A use-after-free in the Linux kernel SMB Direct module allows attackers to cause a system crash or potentially execute code via race conditions.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-90173, GHSA-c82p-5m8q-6jh9, UBUNTU-CVE-2026-90173

## What is CVE-2026-90173?

CVE-2026-90173 is a critical use after free vulnerability in Linux, published on 17 Sep 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:

smb: smbdirect: free completion queues with ib_free_cq()

smbdirect_connection_destroy_qp() creates the send and receive completion
queues with ib_alloc_cq_any(), which for IB_POLL_WORKQUEUE arms an
internal completion handler that runs ib_cq_poll_work() on a workqueue.
Tearing those CQs down with ib_destroy_cq() frees them without first
cancelling that poll work.

If the provider posts a completion late -- for example Soft-RoCE (rxe)
posting an RNR error from rxe_receiver() after rdma_destroy_qp() -- the
handler re-queues ib_cq_poll_work() on the already-freed CQ, and a
follow-on access faults in rxe_req_notify_cq().

Use ib_free_cq(), which cancel_work_sync()es the poll work before freeing
the CQ, so no completion handler can run against a freed queue.

[ 1236.599526] ==================================================================
[ 1236.602142] BUG: KASAN: slab-use-after-free in ib_cq_poll_work+0xd0/0x1a0
[ 1236.605524] Read of size 8 at addr ffff888111865800 by task kworker/4:1H/82
[ 1236.609017]
[ 1236.609270] CPU: 4 UID: 0 PID: 82 Comm: kworker/4:1H Not tainted 7.2.0-rc3-next-20260717-virtme #110 PREEMPT(lazy)
[ 1236.609287] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
[ 1236.609498] Workqueue: ib-comp-wq ib_cq_poll_work
[ 1236.609525] Call Trace:
[ 1236.609536]  <TASK>
[ 1236.609545]  __dump_stack+0x21/0x60
[ 1236.609562]  dump_stack_lvl+0xc2/0x100
[ 1236.609573]  print_address_description+0x77/0x200
[ 1236.609587]  ? ib_cq_poll_work+0xd0/0x1a0
[ 1236.609597]  print_report+0x58/0x70
[ 1236.609607]  kasan_report+0x117/0x150
[ 1236.609623]  ? ib_cq_poll_work+0xd0/0x1a0
[ 1236.609636]  ? process_scheduled_works+0x954/0x1600
[ 1236.609650]  ib_cq_poll_work+0xd0/0x1a0
[ 1236.609662]  ? process_scheduled_works+0x954/0x1600
[ 1236.609674]  process_scheduled_works+0xc22/0x1600
[ 1236.609698]  ? __pfx_process_scheduled_works+0x10/0x10
[ 1236.609713]  ? __pfx_assign_work+0x10/0x10
[ 1236.609726]  ? lock_is_held_type+0x7b/0x110
[ 1236.609741]  worker_thread+0x975/0xee0
[ 1236.609757]  ? __pfx_do_raw_spin_lock+0x10/0x10
[ 1236.609775]  ? __kthread_parkme+0x21e/0x260
[ 1236.609789]  kthread+0x3a6/0x490
[ 1236.609800]  ? __pfx_worker_thread+0x10/0x10
[ 1236.609809]  ? __pfx_kthread+0x10/0x10
[ 1236.609820]  ret_from_fork+0x55a/0xa20
[ 1236.609835]  ? __pfx_ret_from_fork+0x10/0x10
[ 1236.609850]  ? __pfx_kthread+0x10/0x10
[ 1236.609861]  ret_from_fork_asm+0x1a/0x30
[ 1236.609880]  </TASK>
[ 1236.609886]
[ 1236.661292] Allocated by task 5076:
[ 1236.662640]  kasan_save_track+0x3e/0x80
[ 1236.663842]  __kasan_kmalloc+0x72/0x90
[ 1236.664763]  __kmalloc_noprof+0x2b0/0x5d0
[ 1236.665356]  __ib_alloc_cq+0x284/0x1000
[ 1236.666573]  __ib_alloc_cq_any+0x23e/0x340
[ 1236.668654]  smbdirect_connection_create_qp+0x6f7/0x1070
[ 1236.669757]  smbdirect_accept_connect_request+0x500/0x1ca0
[ 1236.672625]  smbdirect_listen_rdma_event_handler+0x1655/0x1c50
[ 1236.673930]  cma_listen_handler+0x1bf/0x260
[ 1236.674923]  cma_cm_event_handler+0x128/0x380
[ 1236.676926]  cma_ib_req_handler+0x2d3d/0x4de0
[ 1236.678368]  cm_process_work+0xb0/0x530
[ 1236.680454]  cm_queue_work_unlock+0xb1/0x230
[ 1236.681673]  cm_work_handler+0x969f/0xdca0
[ 1236.682704]  process_scheduled_works+0xc22/0x1600
[ 1236.683447]  worker_thread+0x975/0xee0
[ 1236.685901]  kthread+0x3a6/0x490
[ 1236.688164]  ret_from_fork+0x55a/0xa20
[ 1236.689522]  ret_from_fork_asm+0x1a/0x30
[ 1236.690073]
[ 1236.690378] Freed by task 5137:
[ 1236.692242]  kasan_save_track+0x3e/0x80
[ 1236.694272]  kasan_save_free_info+0x40/0x50
[ 1236.695514]  __kasan_slab_free+0x3a/0x60
[ 1236.696773]  kfree+0x14e/0x4e0
[ 1236.697216]  ib_destroy_cq_user+0x18d/0x250
[ 1236.699817]  smbdirect_connection_destroy_qp+0xf2/0x280
[ 1236.702115]  smbdirect_socket_destroy_sync+0x1607/0x2720
[ 1236.704062]  smbdirect_socket_release+0x140/0x280
[ 1236.705286]  smb_direct_free_transpor
---truncated---

## Which versions are affected by CVE-2026-90173?


## How do I fix CVE-2026-90173?

Apply the vendor's patch.

## Is CVE-2026-90173 being exploited?

There is no known exploitation of CVE-2026-90173 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90173 and fix it if it is affected.

What it is: CVE-2026-90173 is a critical use after free vulnerability in Linux, published on 17 Sep 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-2026-90173 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-2026-90173/ (Markdown: https://insights.sbomify.com/CVE-2026-90173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90173
- OSV: https://osv.dev/vulnerability/CVE-2026-90173

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90173/
Summaries are generated and may contain mistakes; the official description above is the record.