# CVE-2026-52909: ip6_vti: set netns_immutable on the fallback device.

> Attackers can move the ip6_vti0 fallback tunnel device to another network namespace, bypassing isolation controls and potentially escalating 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:** 19 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-91370, BELL-CVE-2026-52909, DEBIAN-CVE-2026-52909, GHSA-4q3h-784r-7xp4, ROOT-OS-DEBIAN-11-CVE-2026-52909, ROOT-OS-DEBIAN-12-CVE-2026-52909, ROOT-OS-UBUNTU-2204-CVE-2026-52909, ROOT-OS-UBUNTU-2404-CVE-2026-52909, UBUNTU-CVE-2026-52909

## What is CVE-2026-52909?

CVE-2026-52909 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jun 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:

ip6_vti: set netns_immutable on the fallback device.

john1988 and Noam Rathaus reported that vti6_init_net() does not set the
netns_immutable flag on the per-netns fallback tunnel device (ip6_vti0).

Other similar tunnel drivers (like ip6_tunnel, sit, ip6_gre, and ip_tunnel)
correctly set this flag during their fallback device initialization to
prevent them from being moved to another network namespace.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-52909?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52909?

Apply the vendor's patch.

## Is CVE-2026-52909 being exploited?

There is no known exploitation of CVE-2026-52909 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-2026-52909 and fix it if it is affected.

What it is: CVE-2026-52909 is a high-severity missing authorization vulnerability in Linux kernel, published on 19 Jun 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-2026-52909 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-2026-52909/ (Markdown: https://insights.sbomify.com/CVE-2026-52909/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52909
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52909
- OSV: https://osv.dev/vulnerability/CVE-2026-52909

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52909/
Summaries are generated and may contain mistakes; the official description above is the record.