# CVE-2026-98031: nexthop: Initialize extack in remove_nh_grp_entry()

> A null pointer dereference in the Linux kernel nexthop module allows local attackers to cause a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104643, BELL-CVE-2026-98031, DEBIAN-CVE-2026-98031, GHSA-22qv-h2jq-2xcf, UBUNTU-CVE-2026-98031

## What is CVE-2026-98031?

CVE-2026-98031 is a vulnerability in Linux, published on 25 Sep 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:

nexthop: Initialize extack in remove_nh_grp_entry()

remove_nh_grp_entry() prints the extack message when a listener fails
to replace the reduced nexthop group. However, extack is not
initialized and listeners are not required to set a message when
returning an error. Neither netdevsim nor mlxsw do so when an
allocation fails, resulting in the dereference of an uninitialized
stack pointer.

Fix by zero-initializing extack, as was done in commit 6347c5314cee
("nexthop: initialize extack in nh_res_bucket_migrate()").

## Which versions are affected by CVE-2026-98031?


## How do I fix CVE-2026-98031?

Apply the vendor's patch.

## Is CVE-2026-98031 being exploited?

There is no known exploitation of CVE-2026-98031 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98031 and fix it if it is affected.

What it is: CVE-2026-98031 is a vulnerability in Linux, published on 25 Sep 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-2026-98031 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-2026-98031/ (Markdown: https://insights.sbomify.com/CVE-2026-98031/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98031
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98031
- OSV: https://osv.dev/vulnerability/CVE-2026-98031

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98031/
Summaries are generated and may contain mistakes; the official description above is the record.