# CVE-2026-74496: fou: Fix use-after-free in fou_create()

> A use-after-free in the Linux kernel's FOU module allows attackers to potentially execute code or escalate privileges via concurrent socket operations.

- **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:** 16 Oct 2026
- **Also known as:** AZL-96213, BELL-CVE-2026-74496, DEBIAN-CVE-2026-74496, GHSA-p6w2-3hc3-fx3j, UBUNTU-CVE-2026-74496

## What is CVE-2026-74496?

CVE-2026-74496 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:

fou: Fix use-after-free in fou_create()

fou_create() publishes struct fou through sk_user_data before adding the
new FOU port to the per-netns list.  If fou_add_to_port_list() fails,
the error path frees fou while it is still reachable through
sk_user_data.  A concurrent receive can then dereference the freed
object in fou_from_sock().

This ordering issue was previously noted in the linked discussion.

The failure is reachable when local port 0 is requested.  Each socket
binds to a different ephemeral port, but fou_cfg_cmp() compares the
requested port 0 and reports -EALREADY once an entry already exists.

Release the tunnel socket before freeing fou so sk_user_data is cleared
first, and defer reclamation with kfree_rcu() to protect concurrent RCU
readers.  This matches the lifetime handling in fou_release().

## Which versions are affected by CVE-2026-74496?


## How do I fix CVE-2026-74496?

Apply the vendor's patch.

## Is CVE-2026-74496 being exploited?

There is no known exploitation of CVE-2026-74496 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74496 and fix it if it is affected.

What it is: CVE-2026-74496 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-2026-74496 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-2026-74496/ (Markdown: https://insights.sbomify.com/CVE-2026-74496/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74496
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74496
- OSV: https://osv.dev/vulnerability/CVE-2026-74496

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74496/
Summaries are generated and may contain mistakes; the official description above is the record.