# CVE-2026-43127: ntfs3: fix circular locking dependency in run_unpack_ex

> A circular locking dependency in the Linux kernel ntfs3 driver can cause a deadlock, leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 6 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-85797, BELL-CVE-2026-43127, DEBIAN-CVE-2026-43127, GHSA-pmpx-w3f2-x2vp, ROOT-OS-DEBIAN-11-CVE-2026-43127, ROOT-OS-DEBIAN-12-CVE-2026-43127, ROOT-OS-DEBIAN-13-CVE-2026-43127, ROOT-OS-UBUNTU-2204-CVE-2026-43127, ROOT-OS-UBUNTU-2404-CVE-2026-43127, UBUNTU-CVE-2026-43127

## What is CVE-2026-43127?

CVE-2026-43127 is a medium-severity vulnerability in Linux kernel, published on 6 May 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:

ntfs3: fix circular locking dependency in run_unpack_ex

Syzbot reported a circular locking dependency between wnd->rw_lock
(sbi->used.bitmap) and ni->file.run_lock.

The deadlock scenario:
1. ntfs_extend_mft() takes ni->file.run_lock then wnd->rw_lock.
2. run_unpack_ex() takes wnd->rw_lock then tries to acquire
   ni->file.run_lock inside ntfs_refresh_zone().

This creates an AB-BA deadlock.

Fix this by using down_read_trylock() instead of down_read() when
acquiring run_lock in run_unpack_ex(). If the lock is contended,
skip ntfs_refresh_zone() - the MFT zone will be refreshed on the
next MFT operation. This breaks the circular dependency since we
never block waiting for run_lock while holding wnd->rw_lock.

Weakness: CWE-667 (Improper Locking)

## Which versions are affected by CVE-2026-43127?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43127?

Apply the vendor's patch.

## Is CVE-2026-43127 being exploited?

There is no known exploitation of CVE-2026-43127 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43127 and fix it if it is affected.

What it is: CVE-2026-43127 is a medium-severity vulnerability in Linux kernel, published on 6 May 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-2026-43127 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43127/ (Markdown: https://insights.sbomify.com/CVE-2026-43127/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43127
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43127
- OSV: https://osv.dev/vulnerability/CVE-2026-43127

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43127/
Summaries are generated and may contain mistakes; the official description above is the record.