CVE-2026-63917ip6: vti: Use ip6_tnl.net in vti6_changelink().

Official description

In the Linux kernel, the following vulnerability has been resolved: ip6: vti: Use ip6_tnl.net in vti6_changelink(). ip netns add ns1 ip netns add ns2 ip -n ns1 link add vti6_test type vti6 remote ::1 local ::2 key 7 ip -n ns1 link set vti6_test netns ns2 ip -n ns2 link set vti6_test type vti6 remote ::3 local ::4 key 9 ip netns del ns2 ip netns del ns1 [ 132.495484] ------------[ cut here ]------------ [ 132.497609] kernel BUG at net/core/dev.c:12376! Commit 61220ab34948 ("vti6: Enable namespace changing") dropped NETIF_F_NETNS_LOCAL from vti6 devices. A vti6 tunnel can then move through IFLA_NET_NS_FD. After the move dev_net(dev) points at the new netns while t->net stays at the creation netns. vti6_changelink() and vti6_update() still use dev_net(dev) and dev_net(t->dev). They unlink from one per netns hash and relink into another. The creation netns is left with a stale entry. cleanup_net() of that netns later walks freed memory. Reachable from an unprivileged user namespace (unshare --user --map-root-user --net). Cross tenant scope on container hosts.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/0cdce7618464f7fb06f461e8f4ad575cb1d570f4
• https://git.kernel.org/stable/c/f5c68875e25f331e497ddfbe81e2d8163a87f136
• https://git.kernel.org/stable/c/d9c5eecdb3c740e65038651db7c686b10d76d1bc
• https://git.kernel.org/stable/c/f1e89a943ee574d0f2f16246eb3f2d7330fdeb03
• https://git.kernel.org/stable/c/225b467e3b631f38be22e4b38062a1fed02fdd21
• https://git.kernel.org/stable/c/fc32be9ac2788524c6b24efd681cce7a6e731a92
• https://git.kernel.org/stable/c/ee1778ba0f5cb53be771f97017d01eb356c797bf
• https://git.kernel.org/stable/c/11b326fb0a374f4654f9be22d0f0f7abd9f7d3fe