# 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.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97799, BELL-CVE-2026-74744, DEBIAN-CVE-2026-74744, GHSA-cvmj-7cw8-3rr5, UBUNTU-CVE-2026-74744

## 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.

## Is CVE-2026-74744 being exploited?

There is no known exploitation of CVE-2026-74744 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74744 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-74744 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74744/ (Markdown: https://insights.sbomify.com/CVE-2026-74744/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74744
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74744
- OSV: https://osv.dev/vulnerability/CVE-2026-74744

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74744/
Summaries are generated and may contain mistakes; the official description above is the record.