# CVE-2026-98623: drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

> A local attacker with debugfs access can trigger an out-of-bounds read in the nouveau driver, potentially causing a kernel crash or information disclosure.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108626, BELL-CVE-2026-98623, DEBIAN-CVE-2026-98623, GHSA-5c9q-m24x-7r34, UBUNTU-CVE-2026-98623

## What is CVE-2026-98623?

CVE-2026-98623 is an use after free vulnerability in Linux, published on 18 Oct 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:

drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

If list_for_each_entry() exits without hitting a break then "pstate" is
not a valid pstate pointer.  Introduce a "found" variable instead.

The check is reachable from userspace: nvkm_clk_ustate_update() takes the
pstate id straight from the 'pstate' debugfs file, so requesting an id
that is not in clk->states - or any id at all when the perf tables are
broken and the list is empty - makes the pstate->pstate != req test
dereference the list head cast to a struct nvkm_pstate, which is an
out-of-bounds read.

[Francesco: rebased on drm-misc-next, expanded the commit message]

## Which versions are affected by CVE-2026-98623?


## How do I fix CVE-2026-98623?

Apply the vendor's patch.

## Is CVE-2026-98623 being exploited?

There is no known exploitation of CVE-2026-98623 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98623 and fix it if it is affected.

What it is: CVE-2026-98623 is an use after free vulnerability in Linux, published on 18 Oct 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-2026-98623 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-2026-98623/ (Markdown: https://insights.sbomify.com/CVE-2026-98623/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98623
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98623
- OSV: https://osv.dev/vulnerability/CVE-2026-98623

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98623/
Summaries are generated and may contain mistakes; the official description above is the record.