# CVE-2025-21661: gpio: virtuser: fix missing lookup table cleanups

> A memory leak in the Linux kernel's gpio virtuser driver can lead to resource exhaustion and denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-21661, DEBIAN-CVE-2025-21661, GHSA-h85x-rxvw-x49j, UBUNTU-CVE-2025-21661

## What is CVE-2025-21661?

CVE-2025-21661 is a high-severity memory corruption 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:

gpio: virtuser: fix missing lookup table cleanups

When a virtuser device is created via configfs and the probe fails due
to an incorrect lookup table, the table is not removed. This prevents
subsequent probe attempts from succeeding, even if the issue is
corrected, unless the device is released. Additionally, cleanup is also
needed in the less likely case of platform_device_register_full()
failure.

Besides, a consistent memory leak in lookup_table->dev_id was spotted
using kmemleak by toggling the live state between 0 and 1 with a correct
lookup table.

Introduce gpio_virtuser_remove_lookup_table() as the counterpart to the
existing gpio_virtuser_make_lookup_table() and call it from all
necessary points to ensure proper cleanup.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2025-21661?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21661?

Apply the vendor's patch.

## Is CVE-2025-21661 being exploited?

There is no known exploitation of CVE-2025-21661 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-2025-21661 and fix it if it is affected.

What it is: CVE-2025-21661 is a high-severity memory corruption 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-2025-21661 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-2025-21661/ (Markdown: https://insights.sbomify.com/CVE-2025-21661/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21661
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21661
- OSV: https://osv.dev/vulnerability/CVE-2025-21661

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21661/
Summaries are generated and may contain mistakes; the official description above is the record.