# CVE-2026-98786: drm/amd/display: guard dc_sink dereferences in MST mode validation

> A race condition in the Linux kernel AMD display driver allows a local attacker to cause a denial of service via null pointer dereference during MST unplug.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **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-109053, BELL-CVE-2026-98786, DEBIAN-CVE-2026-98786, GHSA-7r8j-xcf8-cxq6, UBUNTU-CVE-2026-98786

## What is CVE-2026-98786?

CVE-2026-98786 is a 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/amd/display: guard dc_sink dereferences in MST mode validation

dm_dp_mst_is_port_support_mode() reads
aconnector->dc_sink->dsc_caps... for the DSC branch-throughput check,
and get_conv_frl_bw()'s HDMI-PCON FRL-bandwidth path reads
aconnector->dc_sink->edid_caps.max_frl_rate, both without a NULL
check. dc_sink is cleared asynchronously on MST unplug, and both
functions run from paths that the driver's own comments document as
racing that teardown: the connector probe worker's ->mode_valid
callback and a compositor's atomic check, neither of which holds the
MST manager lock that the teardown path uses. The former does have an
existing dsc_aux NULL check, but dsc_aux isn't reliably cleared in
every path that clears dc_sink, so it doesn't cover this.

Fail the port-support check and skip the FRL conversion path when the
sink is already gone.

(cherry picked from commit 7c3db8da4e039698ae198c870712428644e965c7)

## Which versions are affected by CVE-2026-98786?


## How do I fix CVE-2026-98786?

Apply the vendor's patch.

## Is CVE-2026-98786 being exploited?

There is no known exploitation of CVE-2026-98786 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98786 and fix it if it is affected.

What it is: CVE-2026-98786 is a 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-2026-98786 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-2026-98786/ (Markdown: https://insights.sbomify.com/CVE-2026-98786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98786
- OSV: https://osv.dev/vulnerability/CVE-2026-98786

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98786/
Summaries are generated and may contain mistakes; the official description above is the record.