# CVE-2026-31509: nfc: nci: fix circular locking dependency in nci_close_device

> A circular locking dependency in the Linux kernel NFC 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:** 22 Apr 2026
- **Updated:** 11 May 2026
- **Also known as:** AZL-83336, BELL-CVE-2026-31509, DEBIAN-CVE-2026-31509, GHSA-x33w-8476-hwm3, ROOT-OS-DEBIAN-11-CVE-2026-31509, ROOT-OS-DEBIAN-12-CVE-2026-31509, ROOT-OS-UBUNTU-2204-CVE-2026-31509, ROOT-OS-UBUNTU-2404-CVE-2026-31509, UBUNTU-CVE-2026-31509

## What is CVE-2026-31509?

CVE-2026-31509 is a medium-severity vulnerability in Linux kernel, published on 22 Apr 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:

nfc: nci: fix circular locking dependency in nci_close_device

nci_close_device() flushes rx_wq and tx_wq while holding req_lock.
This causes a circular locking dependency because nci_rx_work()
running on rx_wq can end up taking req_lock too:

  nci_rx_work -> nci_rx_data_packet -> nci_data_exchange_complete
    -> __sk_destruct -> rawsock_destruct -> nfc_deactivate_target
    -> nci_deactivate_target -> nci_request -> mutex_lock(&ndev->req_lock)

Move the flush of rx_wq after req_lock has been released.
This should safe (I think) because NCI_UP has already been cleared
and the transport is closed, so the work will see it and return
-ENETDOWN.

NIPA has been hitting this running the nci selftest with a debug
kernel on roughly 4% of the runs.

Weakness: CWE-667 (Improper Locking)

## Which versions are affected by CVE-2026-31509?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31509?

Apply the vendor's patch.

## Is CVE-2026-31509 being exploited?

There is no known exploitation of CVE-2026-31509 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-2026-31509 and fix it if it is affected.

What it is: CVE-2026-31509 is a medium-severity vulnerability in Linux kernel, published on 22 Apr 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-2026-31509 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-2026-31509/ (Markdown: https://insights.sbomify.com/CVE-2026-31509/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31509
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31509
- OSV: https://osv.dev/vulnerability/CVE-2026-31509

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31509/
Summaries are generated and may contain mistakes; the official description above is the record.