# CVE-2026-53013: macvlan: fix macvlan_get_size() not reserving space for IFLA_MACVLAN_BC_CUTOFF

> A missing size calculation in the Linux kernel macvlan driver causes netlink dump failures, preventing interface status retrieval when broadcast cutoff is configured.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** Yes
- **Published:** 24 Jun 2026
- **Updated:** 24 Jun 2026
- **Also known as:** BELL-CVE-2026-53013, DEBIAN-CVE-2026-53013, GHSA-mh75-v23p-mcvc, ROOT-OS-UBUNTU-2404-CVE-2026-53013, UBUNTU-CVE-2026-53013

## What is CVE-2026-53013?

CVE-2026-53013 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Jun 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:

macvlan: fix macvlan_get_size() not reserving space for IFLA_MACVLAN_BC_CUTOFF

macvlan_get_size() does not account for IFLA_MACVLAN_BC_CUTOFF, but
macvlan_fill_info() conditionally includes it when port->bc_cutoff != 1.
This causes nla_put_s32() to fail with -EMSGSIZE when the netlink skb
runs out of space, triggering a WARN_ON in rtnetlink and preventing the
interface from being dumped.

The bug can be reproduced with:

  ip link add macvlan0 link eth0 type macvlan mode bridge
  ip link set macvlan0 type macvlan bc_cutoff 0
  ip -d link show macvlan0   # fails with -EMSGSIZE

The bc_cutoff feature was added in commit 954d1fa1ac93 ("macvlan: Add
netlink attribute for broadcast cutoff"), which added the nla_put_s32()
call in macvlan_fill_info() but missed adding the corresponding
nla_total_size(4) in macvlan_get_size(). A follow-up commit
55cef78c244d ("macvlan: add forgotten nla_policy for
IFLA_MACVLAN_BC_CUTOFF") fixed the missing nla_policy entry but still
did not fix the size calculation.

## Which versions are affected by CVE-2026-53013?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53013?

Apply the vendor's patch.

## Is CVE-2026-53013 being exploited?

There is no known exploitation of CVE-2026-53013 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53013 and fix it if it is affected.

What it is: CVE-2026-53013 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-53013 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-53013/ (Markdown: https://insights.sbomify.com/CVE-2026-53013/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53013
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53013
- OSV: https://osv.dev/vulnerability/CVE-2026-53013

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53013/
Summaries are generated and may contain mistakes; the official description above is the record.