# CVE-2026-80580: fbdev: bound mode sysfs output to the sysfs buffer

> A buffer overflow in the Linux kernel fbdev sysfs interface can cause a denial of service when displaying long modelists.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97809, BELL-CVE-2026-80580, DEBIAN-CVE-2026-80580, GHSA-28cj-v8rj-mq63, UBUNTU-CVE-2026-80580

## What is CVE-2026-80580?

CVE-2026-80580 is a high-severity denial of service vulnerability in Linux, published on 26 Aug 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: bound mode sysfs output to the sysfs buffer

mode_string() uses snprintf() which can return a value larger than the
remaining buffer space. show_modes() accumulates the return value into i
without checking whether i has reached PAGE_SIZE, causing the offset to
advance past the sysfs buffer if the modelist is long enough.

Add a size parameter to mode_string() and use scnprintf() to return
only the bytes actually written. Add an early return when offset
already exceeds the buffer. In show_modes(), stop accumulating once
the buffer is full.

## Which versions are affected by CVE-2026-80580?


## How do I fix CVE-2026-80580?

Apply the vendor's patch.

## Is CVE-2026-80580 being exploited?

There is no known exploitation of CVE-2026-80580 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80580 and fix it if it is affected.

What it is: CVE-2026-80580 is a high-severity denial of service vulnerability in Linux, published on 26 Aug 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-2026-80580 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-2026-80580/ (Markdown: https://insights.sbomify.com/CVE-2026-80580/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80580
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80580
- OSV: https://osv.dev/vulnerability/CVE-2026-80580

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80580/
Summaries are generated and may contain mistakes; the official description above is the record.