# CVE-2025-40106: comedi: fix divide-by-zero in comedi_buf_munge()

> A local attacker can cause a kernel panic via divide-by-zero in the comedi driver by submitting a command with a zero channel list length.

- **Severity:** Not scored
- **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:** 31 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40106, DEBIAN-CVE-2025-40106, GHSA-6hvg-fq9h-5pm6, ROOT-OS-DEBIAN-11-CVE-2025-40106, ROOT-OS-DEBIAN-12-CVE-2025-40106, ROOT-OS-DEBIAN-13-CVE-2025-40106, ROOT-OS-UBUNTU-2204-CVE-2025-40106, ROOT-OS-UBUNTU-2404-CVE-2025-40106, UBUNTU-CVE-2025-40106

## What is CVE-2025-40106?

CVE-2025-40106 is a denial of service vulnerability in Linux, published on 31 Oct 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:

comedi: fix divide-by-zero in comedi_buf_munge()

The comedi_buf_munge() function performs a modulo operation
`async->munge_chan %= async->cmd.chanlist_len` without first
checking if chanlist_len is zero. If a user program submits a command with
chanlist_len set to zero, this causes a divide-by-zero error when the device
processes data in the interrupt handler path.

Add a check for zero chanlist_len at the beginning of the
function, similar to the existing checks for !map and
CMDF_RAWDATA flag. When chanlist_len is zero, update
munge_count and return early, indicating the data was
handled without munging.

This prevents potential kernel panics from malformed user commands.

## Which versions are affected by CVE-2025-40106?


## How do I fix CVE-2025-40106?

Apply the vendor's patch.

## Is CVE-2025-40106 being exploited?

There is no known exploitation of CVE-2025-40106 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40106 and fix it if it is affected.

What it is: CVE-2025-40106 is a denial of service vulnerability in Linux, published on 31 Oct 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-2025-40106 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-2025-40106/ (Markdown: https://insights.sbomify.com/CVE-2025-40106/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40106
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40106
- OSV: https://osv.dev/vulnerability/CVE-2025-40106

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40106/
Summaries are generated and may contain mistakes; the official description above is the record.