# CVE-2026-72471: fs/ntfs3: prevent potential lcn remains uninitialized

> An uninitialized variable in the Linux kernel NTFS3 driver can cause a kernel crash when seeking data, leading to denial of service.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **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-2026-72471, GHSA-w848-j2vg-qxfr, UBUNTU-CVE-2026-72471

## What is CVE-2026-72471?

CVE-2026-72471 is a high-severity vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

fs/ntfs3: prevent potential lcn remains uninitialized

The target VCN being sought was not found within runs[0], causing
run_lookup() to return false. This causes run_lookup_entry() to return
false, which in turn results in a len value of 0, and the new parameter
passed to attr_data_get_block() is NULL. Collectively, these factors
ultimately cause attr_data_get_block_locked() to exit prematurely without
initializing lcn, thereby triggering [1].

To prevent [1], the clen check within ni_seek_data_or_hole() has been
moved to occur before the lcn check.

[1]
BUG: KMSAN: uninit-value in ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]

## Which versions are affected by CVE-2026-72471?


## How do I fix CVE-2026-72471?

Apply the vendor's patch.

## Is CVE-2026-72471 being exploited?

There is no known exploitation of CVE-2026-72471 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72471 and fix it if it is affected.

What it is: CVE-2026-72471 is a high-severity vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72471 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-2026-72471/ (Markdown: https://insights.sbomify.com/CVE-2026-72471/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72471
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72471
- OSV: https://osv.dev/vulnerability/CVE-2026-72471

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72471/
Summaries are generated and may contain mistakes; the official description above is the record.