CVE-2026-80838

/// Technical description

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 vxlan_fdb_dst_destroy() and only afterwards tells vxlan_flush()

to destroy the parent FDB entry.

An RCU reader can find the parent during this interval.

first_remote_rcu() then applies list_entry_rcu() 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. vxlan_fdb_destroy() keeps

the remote attached while sending the deletion notification and removing

the parent from the lookup structures.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References