# CVE-2025-21943: gpio: aggregator: protect driver attr handlers against module unload

> A race condition in the Linux kernel GPIO aggregator driver allows local attackers to cause system instability or crashes by triggering module unload during device registration.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/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 Apr 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-59748, AZL-59912, BELL-CVE-2025-21943, DEBIAN-CVE-2025-21943, GHSA-m7pp-g2rm-wrcq, UBUNTU-CVE-2025-21943

## What is CVE-2025-21943?

CVE-2025-21943 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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:

gpio: aggregator: protect driver attr handlers against module unload

Both new_device_store and delete_device_store touch module global
resources (e.g. gpio_aggregator_lock). To prevent race conditions with
module unload, a reference needs to be held.

Add try_module_get() in these handlers.

For new_device_store, this eliminates what appears to be the most dangerous
scenario: if an id is allocated from gpio_aggregator_idr but
platform_device_register has not yet been called or completed, a concurrent
module unload could fail to unregister/delete the device, leaving behind a
dangling platform device/GPIO forwarder. This can result in various issues.
The following simple reproducer demonstrates these problems:

  #!/bin/bash
  while :; do
    # note: whether 'gpiochip0 0' exists or not does not matter.
    echo 'gpiochip0 0' > /sys/bus/platform/drivers/gpio-aggregator/new_device
  done &
  while :; do
    modprobe gpio-aggregator
    modprobe -r gpio-aggregator
  done &
  wait

  Starting with the following warning, several kinds of warnings will appear
  and the system may become unstable:

  ------------[ cut here ]------------
  list_del corruption, ffff888103e2e980->next is LIST_POISON1 (dead000000000100)
  WARNING: CPU: 1 PID: 1327 at lib/list_debug.c:56 __list_del_entry_valid_or_report+0xa3/0x120
  [...]
  RIP: 0010:__list_del_entry_valid_or_report+0xa3/0x120
  [...]
  Call Trace:
   <TASK>
   ? __list_del_entry_valid_or_report+0xa3/0x120
   ? __warn.cold+0x93/0xf2
   ? __list_del_entry_valid_or_report+0xa3/0x120
   ? report_bug+0xe6/0x170
   ? __irq_work_queue_local+0x39/0xe0
   ? handle_bug+0x58/0x90
   ? exc_invalid_op+0x13/0x60
   ? asm_exc_invalid_op+0x16/0x20
   ? __list_del_entry_valid_or_report+0xa3/0x120
   gpiod_remove_lookup_table+0x22/0x60
   new_device_store+0x315/0x350 [gpio_aggregator]
   kernfs_fop_write_iter+0x137/0x1f0
   vfs_write+0x262/0x430
   ksys_write+0x60/0xd0
   do_syscall_64+0x6c/0x180
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
   [...]
   </TASK>
  ---[ end trace 0000000000000000 ]---

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2025-21943?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21943?

Apply the vendor's patch.

## Is CVE-2025-21943 being exploited?

There is no known exploitation of CVE-2025-21943 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-2025-21943 and fix it if it is affected.

What it is: CVE-2025-21943 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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-2025-21943 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-2025-21943/ (Markdown: https://insights.sbomify.com/CVE-2025-21943/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21943
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21943
- OSV: https://osv.dev/vulnerability/CVE-2025-21943

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21943/
Summaries are generated and may contain mistakes; the official description above is the record.