CVE-2026-98306

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

seg6: set IPSKB L3SLAVE from IP6SKB L3SLAVE on IPIP decapsulation

When an SRv6 packet arrives on an interface enslaved to a VRF, vrf ip6 rcv() sets IP6SKB L3SLAVE in IP6CB, but decap and validate() has never set IPSKB L3SLAVE in IPCB. The bit stayed clear in the common case, and with CONFIG IPV6 MIP6 the leftover frag max size of a reassembled outer packet could even set it, with no VRF involved. Commit 44930446dde4 ("ipv6: seg6: clear IPv4 control block on IPIP decapsulation") then made the unreliable bit reliably clear.

The effect of the missing flag is visible with End.DX4 when a delivery to a local address of the node reaches the socket lookup. For example, a UDP socket bound to the enslaved ingress interface does not receive any of the decapsulated packets, while an unbound socket outside the VRF does. This contradicts Documentation/networking/vrf.rst: by default the scope of an unbound UDP or TCP socket is limited to the default VRF.

Set IPSKB L3SLAVE for IPv4 in decap and validate(), which already does the same for IPv6. The socket lookup then matches the decapsulated packet like any other packet received on that enslaved interface. Such a packet matches an unbound UDP or TCP socket only when udp l3mdev accept or tcp l3mdev accept is set.