CVE-2026-63921

In the Linux kernel, the following vulnerability has been resolved: ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate(). After patch 1/2 in this series, vti6_update() unlinks and relinks the tunnel through t->net. vti6_siocdevprivate() still uses dev_net(dev) for the collision lookup. For a tunnel moved through IFLA_NET_NS_FD, dev_net(dev) is the new netns, not t->net. SIOCCHGTUNNEL on a migrated tunnel then runs: net = dev_net(dev) /* migrated netns */ t = vti6_locate(net, &p1, false) /* misses target in t->net */ ... t = netdev_priv(dev) vti6_update(t, &p1, false) /* mutates t->net's hash */ A caller in the migrated netns picks params that match a tunnel in the creation netns. The lookup in dev_net(dev) finds nothing. vti6_update() prepends the migrated tunnel at the head of the creation netns hash bucket for those params. Later lookups in the creation netns resolve to the migrated device. xfrm receive delivers the matched packets through a device the caller controls. Reachable from an unprivileged user namespace (unshare --user --map-root-user --net). Cross tenant scope on container hosts. Switch the SIOCCHGTUNNEL path on a non fallback device to use t->net for the lookup. The lookup now matches the netns vti6_update() operates on. Also add ns_capable(self->net->user_ns, CAP_NET_ADMIN) before the lookup. The check at the top of the case is against dev_net(dev)->user_ns, which after migration is the attacker's netns. A caller there can pick params absent from self->net, the lookup returns NULL, t becomes self, and vti6_update() inserts the device into the creation netns hash. The new check requires CAP_NET_ADMIN in the creation netns user_ns too. SIOCADDTUNNEL and SIOCCHGTUNNEL on the fallback device keep dev_net(dev), which equals init_net there.

• https://git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33
• https://git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906
• https://git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab
• https://git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838
• https://git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6
• https://git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941
• https://git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011
• https://git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf

Published

Jul 19, 2026

Last Modified

Jul 27, 2026

Status

Awaiting Analysis

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-63916In the Linux kernel, the following vulnerability has been re…8.8
• CVE-2026-63917In the Linux kernel, the following vulnerability has been re…8.8
• CVE-2026-63918In the Linux kernel, the following vulnerability has been re…7.8
• CVE-2026-63919In the Linux kernel, the following vulnerability has been re…8.8
• CVE-2026-6392Tanium addressed an information disclosure vulnerability in …2.7
• CVE-2026-63920In the Linux kernel, the following vulnerability has been re…7.1
• CVE-2026-63922In the Linux kernel, the following vulnerability has been re…9.8
• CVE-2026-63923In the Linux kernel, the following vulnerability has been re…8.8
• CVE-2026-63924In the Linux kernel, the following vulnerability has been re…9.8
• CVE-2026-63925In the Linux kernel, the following vulnerability has been re…8.1
• CVE-2026-63926In the Linux kernel, the following vulnerability has been re…8.4
• CVE-2026-63927In the Linux kernel, the following vulnerability has been re…7.8