CVE-2026-80996 net: l2tp: do not propagate multicast notification errors
An attacker with local access can cause resource exhaustion in the Linux kernel L2TP module by triggering repeated operations that fail due to notification errors.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80996?
CVE-2026-80996 is a denial of service vulnerability in Linux, published on 11 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:
net: l2tp: do not propagate multicast notification errors
The tunnel create, tunnel modify, session create, and session modify netlink handlers send multicast notifications through helpers that can fail while allocating or encoding a message, or while multicasting it.
For tunnel and session create/modify, a notification is sent after the live operation has completed. Returning a best-effort notification error as the command result can therefore report failure for an operation that already committed and can cause callers to retry and accumulate live objects.
Keep sending notifications for listener visibility, but do not propagate their best-effort status as the command result. This also keeps the tunnel modify command consistent with the other notification-only paths.
Which versions are affected by CVE-2026-80996?
How do I fix CVE-2026-80996?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-80996 being exploited?
There is no known exploitation of CVE-2026-80996 in the wild and no public exploit code.
Sources
Also known as AZL-100832, BELL-CVE-2026-80996, DEBIAN-CVE-2026-80996, GHSA-hc5w-42jx-9cr6, UBUNTU-CVE-2026-80996.