CVE-2026-93204 batman-adv: dat: atomically update mac addresses
A race condition in the Linux kernel batman-adv module allows attackers to poison ARP caches by exploiting non-atomic MAC address updates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93204?
CVE-2026-93204 is a vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: dat: atomically update mac addresses
When a MAC address is updated in batadv_dat_entry_add(), it is done using a simple copy function. A parallel reader might only see parts of this update. In worst case, the reader is transporting the half updated MAC address over the network or is creating an ARP response using it - poisoning the ARP cache.
atomic64_t can be used to store the 48 bit of a mac address. A reader will then either see the old mac address or the new one - never a mixture of both.
Which versions are affected by CVE-2026-93204?
How do I fix CVE-2026-93204?
Apply the vendor's patch.
Is CVE-2026-93204 being exploited?
There is no known exploitation of CVE-2026-93204 in the wild and no public exploit code.
Sources
Also known as AZL-103035, BELL-CVE-2026-93204, DEBIAN-CVE-2026-93204, GHSA-9fhg-rrvj-mjc8, UBUNTU-CVE-2026-93204.