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.
- 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
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
Which versions are affected by CVE-2026-52909?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52909?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
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
Sources
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 and 3 more.