# CVE-2026-31770: hwmon: (occ) Fix division by zero in occ_show_power_1()

> A division by zero in the Linux kernel's OCC power sensor driver causes a crash during early boot if no samples are collected.

- **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:** 1 May 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-31770, DEBIAN-CVE-2026-31770, GHSA-9842-v9gc-hxx2, ROOT-OS-DEBIAN-11-CVE-2026-31770, ROOT-OS-UBUNTU-2204-CVE-2026-31770, ROOT-OS-UBUNTU-2404-CVE-2026-31770, UBUNTU-CVE-2026-31770

## What is CVE-2026-31770?

CVE-2026-31770 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 2026. 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:

hwmon: (occ) Fix division by zero in occ_show_power_1()

In occ_show_power_1() case 1, the accumulator is divided by
update_tag without checking for zero. If no samples have been
collected yet (e.g. during early boot when the sensor block is
included but hasn't been updated), update_tag is zero, causing
a kernel divide-by-zero crash.

The 2019 fix in commit 211186cae14d ("hwmon: (occ) Fix division by
zero issue") only addressed occ_get_powr_avg() used by
occ_show_power_2() and occ_show_power_a0(). This separate code
path in occ_show_power_1() was missed.

Fix this by reusing the existing occ_get_powr_avg() helper, which
already handles the zero-sample case and uses mul_u64_u32_div()
to multiply before dividing for better precision. Move the helper
above occ_show_power_1() so it is visible at the call site.

[groeck: Fix alignment problems reported by checkpatch]

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2026-31770?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31770?

Apply the vendor's patch.

## Is CVE-2026-31770 being exploited?

There is no known exploitation of CVE-2026-31770 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-2026-31770 and fix it if it is affected.

What it is: CVE-2026-31770 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 May 2026. 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-2026-31770 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-2026-31770/ (Markdown: https://insights.sbomify.com/CVE-2026-31770/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31770
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31770
- OSV: https://osv.dev/vulnerability/CVE-2026-31770

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31770/
Summaries are generated and may contain mistakes; the official description above is the record.