# CVE-2026-43238: net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()

> A divide-by-zero error in the Linux kernel's skbedit action can cause a system crash when specific queue mapping ranges are configured.

- **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:** 6 May 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-43238, DEBIAN-CVE-2026-43238, GHSA-76w3-fgp7-3hf7, ROOT-OS-UBUNTU-2404-CVE-2026-43238, UBUNTU-CVE-2026-43238

## What is CVE-2026-43238?

CVE-2026-43238 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 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:

net/sched: act_skbedit: fix divide-by-zero in tcf_skbedit_hash()

Commit 38a6f0865796 ("net: sched: support hash selecting tx queue")
added SKBEDIT_F_TXQ_SKBHASH support. The inclusive range size is
computed as:

mapping_mod = queue_mapping_max - queue_mapping + 1;

The range size can be 65536 when the requested range covers all possible
u16 queue IDs (e.g. queue_mapping=0 and queue_mapping_max=U16_MAX).
That value cannot be represented in a u16 and previously wrapped to 0,
so tcf_skbedit_hash() could trigger a divide-by-zero:

queue_mapping += skb_get_hash(skb) % params->mapping_mod;

Compute mapping_mod in a wider type and reject ranges larger than U16_MAX
to prevent params->mapping_mod from becoming 0 and avoid the crash.

Weakness: CWE-369 (Divide By Zero)

## Which versions are affected by CVE-2026-43238?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43238?

Apply the vendor's patch.

## Is CVE-2026-43238 being exploited?

There is no known exploitation of CVE-2026-43238 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-2026-43238 and fix it if it is affected.

What it is: CVE-2026-43238 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 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-2026-43238 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-2026-43238/ (Markdown: https://insights.sbomify.com/CVE-2026-43238/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43238
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43238
- OSV: https://osv.dev/vulnerability/CVE-2026-43238

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43238/
Summaries are generated and may contain mistakes; the official description above is the record.