CVE-2026-80978 net: cap advertised IP tunnel headroom
A Linux kernel vulnerability allows integer overflow in IP tunnel headroom calculations, potentially causing memory corruption or denial of service.
- 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-2026-80978?
CVE-2026-80978 is a high-severity 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: cap advertised IP tunnel headroom
IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets.
The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device.
Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers.
Which versions are affected by CVE-2026-80978?
How do I fix CVE-2026-80978?
Apply the vendor's patch.
Is CVE-2026-80978 being exploited?
There is no known exploitation of CVE-2026-80978 in the wild and no public exploit code.
Sources
Also known as AZL-100806, BELL-CVE-2026-80978, DEBIAN-CVE-2026-80978, GHSA-p2qp-rm9g-w8f3, UBUNTU-CVE-2026-80978.