# CVE-2025-21662: net/mlx5: Fix variable not being completed when function returns

> A bug in the mlx5 network driver causes kernel tasks to hang indefinitely when command allocation fails, 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:** 21 Jan 2025
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2025-21662, DEBIAN-CVE-2025-21662, GHSA-2ww6-2gwx-v942, UBUNTU-CVE-2025-21662

## What is CVE-2025-21662?

CVE-2025-21662 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Jan 2025. 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:

net/mlx5: Fix variable not being completed when function returns

When cmd_alloc_index(), fails cmd_work_handler() needs
to complete ent->slotted before returning early.
Otherwise the task which issued the command may hang:

   mlx5_core 0000:01:00.0: cmd_work_handler:877:(pid 3880418): failed to allocate command entry
   INFO: task kworker/13:2:4055883 blocked for more than 120 seconds.
         Not tainted 4.19.90-25.44.v2101.ky10.aarch64 #1
   "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
   kworker/13:2    D    0 4055883      2 0x00000228
   Workqueue: events mlx5e_tx_dim_work [mlx5_core]
   Call trace:
      __switch_to+0xe8/0x150
      __schedule+0x2a8/0x9b8
      schedule+0x2c/0x88
      schedule_timeout+0x204/0x478
      wait_for_common+0x154/0x250
      wait_for_completion+0x28/0x38
      cmd_exec+0x7a0/0xa00 [mlx5_core]
      mlx5_cmd_exec+0x54/0x80 [mlx5_core]
      mlx5_core_modify_cq+0x6c/0x80 [mlx5_core]
      mlx5_core_modify_cq_moderation+0xa0/0xb8 [mlx5_core]
      mlx5e_tx_dim_work+0x54/0x68 [mlx5_core]
      process_one_work+0x1b0/0x448
      worker_thread+0x54/0x468
      kthread+0x134/0x138
      ret_from_fork+0x10/0x18

## Which versions are affected by CVE-2025-21662?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21662?

Apply the vendor's patch.

## Is CVE-2025-21662 being exploited?

There is no known exploitation of CVE-2025-21662 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-2025-21662 and fix it if it is affected.

What it is: CVE-2025-21662 is a medium-severity denial of service vulnerability in Linux kernel, published on 21 Jan 2025. 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-2025-21662 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-2025-21662/ (Markdown: https://insights.sbomify.com/CVE-2025-21662/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21662
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21662
- OSV: https://osv.dev/vulnerability/CVE-2025-21662

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21662/
Summaries are generated and may contain mistakes; the official description above is the record.