# CVE-2026-72186: ntfs: make system files immutable to prevent corruption

> A local attacker can corrupt NTFS volumes and cause system deadlocks by writing to protected system files, requiring a kernel patch.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72186, GHSA-cpf7-qp55-xqgv, UBUNTU-CVE-2026-72186

## What is CVE-2026-72186?

CVE-2026-72186 is a critical denial of service vulnerability in Linux, published on 15 Aug 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: make system files immutable to prevent corruption

When a system file such as $Bitmap is exposed via show_sys_files and
written from userspace, the volume is corrupted and, because the cluster
allocator scans $Bitmap through the same inode's page cache, a write to
$Bitmap also deadlocks writeback against the folio it already holds locked.

These files are maintained by the driver itself and have no valid reason
to be written through the file interface. Mark base metadata files
(mft_no < FILE_first_user) as immutable during inode read so the VFS
rejects write, mmap, truncate and unlink with -EPERM. Directories are
skipped so the root and $Extend remain usable. Internal metadata updates
do not go through the VFS write path and are unaffected.

## Which versions are affected by CVE-2026-72186?


## How do I fix CVE-2026-72186?

Apply the vendor's patch.

## Is CVE-2026-72186 being exploited?

There is no known exploitation of CVE-2026-72186 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72186 and fix it if it is affected.

What it is: CVE-2026-72186 is a critical denial of service vulnerability in Linux, published on 15 Aug 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-2026-72186 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-2026-72186/ (Markdown: https://insights.sbomify.com/CVE-2026-72186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72186
- OSV: https://osv.dev/vulnerability/CVE-2026-72186

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72186/
Summaries are generated and may contain mistakes; the official description above is the record.