CVE-2026-98568 vxlan: use one headroom snapshot for neighbour replies
A race condition in the Linux kernel VXLAN module allows out-of-bounds writes during neighbour reply generation, potentially leading to code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98568?
CVE-2026-98568 is a vulnerability in Linux, published on 18 Oct 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: use one headroom snapshot for neighbour replies
vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then samples it again to reserve headroom. A concurrent vxlan_changelink() can update needed_headroom between the two reads, creating a TOCTOU race. The second value can exceed the allocation and make the Ethernet header write out of bounds.
The race is reproducible on the unpatched kernel. It occurred when vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte skbuff_small_head allocation.
Snapshot the headroom once and use that value for both allocation and reservation.
Which versions are affected by CVE-2026-98568?
How do I fix CVE-2026-98568?
Apply the vendor's patch.
Is CVE-2026-98568 being exploited?
There is no known exploitation of CVE-2026-98568 in the wild and no public exploit code.
Sources
Also known as AZL-109263, BELL-CVE-2026-98568, DEBIAN-CVE-2026-98568, GHSA-489c-q3cc-mm5r, UBUNTU-CVE-2026-98568.