CVE-2026-68116

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

vxlan: mdb: Fix source list corruption on a failed replace

When replacing the source list of an MDB remote entry, all existing

sources are first marked for deletion and vxlan_mdb_remote_srcs_add()

is then called to add the new source list. Sources present in the new

list have their deletion mark cleared, and any sources left marked

afterwards are removed.

If vxlan_mdb_remote_srcs_add() fails partway through, its error path

deletes all entries on the remote's source list. That rollback is only

correct for its other caller, vxlan_mdb_remote_add(), where the remote

was just allocated and the list contains solely entries added during

the call. On the replace path the list also holds pre-existing sources,

so a failed replace tears them down together with their (S, G)

forwarding entries instead of leaving the entry unchanged.

This is reachable from an existing (*, G) remote. An EXCLUDE filter

that loses sources starts forwarding traffic that should be blocked,

while an INCLUDE filter that loses sources drops traffic that should be

forwarded.

Mark entries created during the current pass with a new

VXLAN_SGRP_F_NEW flag. On failure, delete only those entries and clear

the deletion mark on the pre-existing ones, so a failed replace leaves

the source list untouched. Retain the flag until the whole operation

succeeds and then clear it. Also stop vxlan_mdb_remote_src_add() from

deleting a pre-existing entry it only looked up when adding that

entry's forwarding entry fails.