# CVE-2025-21746: Input: synaptics - fix crash when enabling pass-through port

> A race condition in the Linux kernel Synaptics driver can cause a system crash when enabling a pass-through port.

- **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:** 27 Feb 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-21746, DEBIAN-CVE-2025-21746, GHSA-9964-v64g-g4c3, ROOT-OS-UBUNTU-2404-CVE-2025-21746, UBUNTU-CVE-2025-21746

## What is CVE-2025-21746?

CVE-2025-21746 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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:

Input: synaptics - fix crash when enabling pass-through port

When enabling a pass-through port an interrupt might come before psmouse
driver binds to the pass-through port. However synaptics sub-driver
tries to access psmouse instance presumably associated with the
pass-through port to figure out if only 1 byte of response or entire
protocol packet needs to be forwarded to the pass-through port and may
crash if psmouse instance has not been attached to the port yet.

Fix the crash by introducing open() and close() methods for the port and
check if the port is open before trying to access psmouse instance.
Because psmouse calls serio_open() only after attaching psmouse instance
to serio port instance this prevents the potential crash.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2025-21746?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21746?

Apply the vendor's patch.

## Is CVE-2025-21746 being exploited?

There is no known exploitation of CVE-2025-21746 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-2025-21746 and fix it if it is affected.

What it is: CVE-2025-21746 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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-2025-21746 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-2025-21746/ (Markdown: https://insights.sbomify.com/CVE-2025-21746/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21746
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21746
- OSV: https://osv.dev/vulnerability/CVE-2025-21746

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21746/
Summaries are generated and may contain mistakes; the official description above is the record.