# CVE-2026-72405: net: udp_tunnel: prevent double queueing in udp_tunnel_nic_device_sync

> A race condition in the Linux kernel UDP tunnel driver allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 15 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-96275, BELL-CVE-2026-72405, DEBIAN-CVE-2026-72405, GHSA-w888-j23q-c78g, UBUNTU-CVE-2026-72405

## What is CVE-2026-72405?

CVE-2026-72405 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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:

net: udp_tunnel: prevent double queueing in udp_tunnel_nic_device_sync

Yue Sun reported a use-after-free and debugobjects warning in
udp_tunnel_nic_device_sync_work() during concurrent device operations.

The workqueue core clears the internal pending bit before invoking the
worker. At that point, a concurrent thread can queue the work again.
When the already running worker eventually clears the work_pending flag
to 0, it mistakenly clears the flag for the newly queued instance.
udp_tunnel_nic_unregister() then observes work_pending as 0 and frees
the structure while the second work item is still active in the queue,
leading to UAF.

Fix this by returning early in udp_tunnel_nic_device_sync() if
work_pending is already set, preventing redundant work queueing.

## Which versions are affected by CVE-2026-72405?


## How do I fix CVE-2026-72405?

Apply the vendor's patch.

## Is CVE-2026-72405 being exploited?

There is no known exploitation of CVE-2026-72405 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72405 and fix it if it is affected.

What it is: CVE-2026-72405 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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-2026-72405 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-2026-72405/ (Markdown: https://insights.sbomify.com/CVE-2026-72405/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72405
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72405
- OSV: https://osv.dev/vulnerability/CVE-2026-72405

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72405/
Summaries are generated and may contain mistakes; the official description above is the record.