CVE-2026-80838 vxlan: keep the last remote linked during FDB flush
A race condition in the Linux kernel VXLAN driver allows attackers to trigger a use-after-free, potentially leading to code execution or system crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80838?
CVE-2026-80838 is an use after free vulnerability in Linux, published on 4 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-80838?
How do I fix CVE-2026-80838?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-80838 being exploited?
There is no known exploitation of CVE-2026-80838 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-80838, DEBIAN-CVE-2026-80838, GHSA-9cfq-2rjh-r5vr, UBUNTU-CVE-2026-80838.