CVE-2026-74744 ipvlan: inherit needed_headroom and needed_tailroom from phy_dev
A missing headroom inheritance in Linux kernel ipvlan devices can cause use-after-free crashes, allowing attackers to trigger denial of service or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74744?
CVE-2026-74744 is a critical use after free vulnerability in Linux, published on 26 Aug 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:
ipvlan: inherit needed_headroom and needed_tailroom from phy_dev
ipvlan devices inherit hard_header_len from phy_dev during ipvlan_init(), but leave needed_headroom and needed_tailroom set to 0.
When the underlying phy_dev (or stacked lower device) requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space.
This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / ipvlan_hard_header() prepends header data or when lower devices append tailroom.
Fix this by: 1. Inheriting needed_headroom and needed_tailroom from phy_dev in ipvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached ipvlans in ipvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.
Which versions are affected by CVE-2026-74744?
How do I fix CVE-2026-74744?
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-2026-74744 being exploited?
There is no known exploitation of CVE-2026-74744 in the wild and no public exploit code.
Sources
Also known as AZL-97799, BELL-CVE-2026-74744, DEBIAN-CVE-2026-74744, GHSA-cvmj-7cw8-3rr5, UBUNTU-CVE-2026-74744.