# CVE-2026-80785: fbdev: serialize mode sysfs access with lock_fb_info()

> A use-after-free vulnerability in the Linux kernel's fbdev subsystem allows local attackers to execute arbitrary code or escalate privileges via concurrent sysfs access.

- **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:** 4 Sep 2026
- **Updated:** 7 Sep 2026
- **Also known as:** AZL-99434, BELL-CVE-2026-80785, DEBIAN-CVE-2026-80785, GHSA-9wwr-625v-fr4h, UBUNTU-CVE-2026-80785

## What is CVE-2026-80785?

CVE-2026-80785 is an use after free vulnerability in Linux, published on 4 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:

fbdev: serialize mode sysfs access with lock_fb_info()

show_mode(), show_modes(), and store_mode() access fb_info->modelist
and fb_info->mode without holding lock_fb_info(). store_modes() takes
lock_fb_info() while replacing the modelist and freeing the old one.

A concurrent reader or writer can load a pointer to an old modelist
entry before store_modes() frees it, then dereference freed memory or
store a stale freed pointer in fb_info->mode.

Take lock_fb_info() in show_mode(), show_modes(), and store_mode() to
serialize with store_modes(). In show_mode(), copy the mode to the
stack and format after dropping the lock. In store_mode(), split
activate() into a _locked variant to avoid double-locking, and hold
the locks for the modelist walk, mode conversion, activation, and
fb_info->mode assignment together.

## Which versions are affected by CVE-2026-80785?


## How do I fix CVE-2026-80785?

Apply the vendor's patch.

## Is CVE-2026-80785 being exploited?

There is no known exploitation of CVE-2026-80785 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80785 and fix it if it is affected.

What it is: CVE-2026-80785 is an use after free vulnerability in Linux, published on 4 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-2026-80785 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-2026-80785/ (Markdown: https://insights.sbomify.com/CVE-2026-80785/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80785
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80785
- OSV: https://osv.dev/vulnerability/CVE-2026-80785

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80785/
Summaries are generated and may contain mistakes; the official description above is the record.