# CVE-2026-89745: debugfs: Fix lockdown check for mmap_prepare

> Attackers with high privileges can bypass kernel lockdown integrity checks on debugfs files using mmap_prepare, potentially compromising system integrity.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89745, GHSA-93g4-3jvg-hjgx, UBUNTU-CVE-2026-89745

## What is CVE-2026-89745?

CVE-2026-89745 is a vulnerability in Linux, published on 11 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:

debugfs: Fix lockdown check for mmap_prepare

Commit 651fdda8406d ("relay: update relay to use mmap_prepare")
changed the `mmap` file operation to `mmap_prepare` for relayfs, but
the lockdown check in debugfs was not updated accordingly.

This prevents debugfs from being locked down when the kernel is in
integrity mode if a file uses `mmap_prepare` but not `mmap`.

Since the conversion to `mmap_prepare` across the kernel is not yet
complete, update the lockdown check to look for both `mmap` and
`mmap_prepare` to ensure comprehensive coverage.

## Which versions are affected by CVE-2026-89745?


## How do I fix CVE-2026-89745?

Apply the vendor's patch.

## Is CVE-2026-89745 being exploited?

There is no known exploitation of CVE-2026-89745 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89745 and fix it if it is affected.

What it is: CVE-2026-89745 is a vulnerability in Linux, published on 11 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-2026-89745 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-2026-89745/ (Markdown: https://insights.sbomify.com/CVE-2026-89745/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89745
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89745
- OSV: https://osv.dev/vulnerability/CVE-2026-89745

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89745/
Summaries are generated and may contain mistakes; the official description above is the record.