# CVE-2026-89612: ntfs: reject invalid MFT LCNs from boot sector

> A crafted NTFS image can cause an integer overflow leading to out-of-bounds memory access, potentially crashing the system.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89612, GHSA-v9qj-wpxr-47gc, UBUNTU-CVE-2026-89612

## What is CVE-2026-89612?

CVE-2026-89612 is a critical vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ntfs: reject invalid MFT LCNs from boot sector

The NTFS boot sector stores the MFT and MFTMirr locations as unsigned
64-bit LCNs, but parse_ntfs_boot_sector() decoded them into an s64.

A crafted high-bit value could therefore become negative and pass
the existing upper-bound check. The invalid value then propagated into
the MFT zone allocator and could result in an out-of-bounds access to
lcn_empty_bits_per_page.

## Which versions are affected by CVE-2026-89612?


## How do I fix CVE-2026-89612?

Apply the vendor's patch.

## Is CVE-2026-89612 being exploited?

There is no known exploitation of CVE-2026-89612 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89612 and fix it if it is affected.

What it is: CVE-2026-89612 is a critical vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89612 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-2026-89612/ (Markdown: https://insights.sbomify.com/CVE-2026-89612/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89612
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89612
- OSV: https://osv.dev/vulnerability/CVE-2026-89612

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89612/
Summaries are generated and may contain mistakes; the official description above is the record.