CVE-2026-80838

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

vxlan: keep the last remote linked during FDB flush

A non-nexthop FDB entry is expected to have at least one remote while it remains reachable through the FDB hash table. A filtered bulk flush violates this invariant when every remote matches: It unlinks the last remote in vxlanfdbdstdestroy() and only afterwards tells vxlanflush() to destroy the parent FDB entry.

An RCU reader can find the parent during this interval. firstremotercu() then applies listentryrcu() to the empty list head, producing an invalid remote pointer that the receive learning path can read from and write to.

When a matching remote is the sole remaining remote, leave it linked and ask the caller to destroy the entire FDB entry. vxlanfdbdestroy() keeps the remote attached while sending the deletion notification and removing the parent from the lookup structures.