CVE-2026-46120

In the Linux kernel, the following vulnerability has been resolved:

ip6_gre: Use cached t->net in ip6erspan_changelink().

After commit 5e72ce3e3980 (net: ipv6: Use link netns in newlink() of rtnl_link_ops), ip6erspan_newlink() correctly resolves the per-netns ip6gre hash via link_net. ip6erspan_changelink() was not converted in that series and still uses dev_net(dev), which diverges from the devices creation netns after IFLA_NET_NS_FD migration.

This re-inserts the tunnel into the wrong per-netns hash. The original netns keeps a stale entry. When that netns is later destroyed, ip6gre_exit_rtnl_net() walks the stale entry, producing a slab-use-after-free reported by KASAN, followed by a kernel BUG at net/core/dev.c (LIST_POISON1) in unregister_netdevice_many_notify().

Reachable from an unprivileged user namespace (unshare –user –map-root-user –net).

ip6gre_changelink() earlier in the same file already uses the cached t->net; only ip6erspan_changelink() has the wrong shape.

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 Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.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/01b71ff2857d3598337de11e7840a8e3ff21553c
• https://git.kernel.org/stable/c/0fcf6731706f73494245a9c0d64f93bebf95bb51
• https://git.kernel.org/stable/c/1d324c2f43f70c965f25c58cc3611c779adbe47e
• https://git.kernel.org/stable/c/311fdd26eb4443d43b909cc67a10f3a5fd1b21b2
• https://git.kernel.org/stable/c/7bd0f2b162b426b343a114e1b329f0d8d14fdc6e
• https://git.kernel.org/stable/c/cf7fc624329e76c6394653d12353e1d033adea91
• https://git.kernel.org/stable/c/e70cfb40c3a99b232cd42c6a6a10f0d8e039dc82
• https://git.kernel.org/stable/c/eca62bb0569de4d43a4dac06a2092a9d4ca1d702