CVE-2026-63917

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.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

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