Linux KernelOperating system · Linux

CVE-2026-53013

MEDIUM · 5.5 CVSS v3.1 Published 2026-06-24

Fix available

A fix is available. Upgrade to 6.6.141 / 6.12.91 or later.

See remediation →

57/100

Remediation priority · Elevated

Zero-click Patch available 8 weeks old

Official description

NVD · unedited

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.

Technical summary

dbcve analysis · high confidence

In the Linux kernel macvlan driver, the macvlan_get_size() function fails to reserve space for the IFLA_MACVLAN_BC_CUTOFF netlink attribute, while macvlan_fill_info() conditionally includes it when port->bc_cutoff != 1. This causes nla_put_s32() to fail with -EMSGSIZE when the netlink message buffer is too small, triggering a WARN_ON in rtnetlink and preventing the interface from being dumped via 'ip -d link show'.

MitigationApply the kernel patch that adds nla_total_size(4) to macvlan_get_size() to properly reserve space for the IFLA_MACVLAN_BC_CUTOFF attribute, or upgrade to a kernel version containing the fix.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions

NVD · CPE data

Linux KernelOperating system

Affected:>= 6.4, < 6.6.141>= 6.7, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10

CVSS breakdown

From the vector

Attack vector: Local
Complexity: Low
Privileges: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected?

dbcve checks

Work through these to decide whether this CVE applies to you.

Check kernel version

Run 'uname -r' or 'cat /proc/version' to obtain the installed kernel version

Affected if The kernel version falls within any of these ranges: >= 6.4 and < 6.6.141, >= 6.7 and < 6.12.91, >= 6.13 and < 6.18.33, or >= 6.19 and < 7.0.10
Verify macvlan interfaces exist

Run 'ip link show' and filter for interfaces with 'macvlan' in the output, or use 'ip link show type macvlan'

Affected if There are macvlan interfaces configured on the system
Check bc_cutoff setting on macvlan ports

Use 'ip -d link show' to dump interface details. Look for the 'bc_cutoff' value in the output. If not visible, check /sys/class/net/<interface>/master or use 'ip link set dev <name> master' to verify the port configuration

Affected if The macvlan port has bc_cutoff set to a value other than 1 (the default is 1, which does not trigger the bug because the attribute is not included)
Trigger the failure condition

Run 'ip -d link show' for a specific macvlan interface: 'ip -d link show dev <macvlan_iface>'. If the interface has bc_cutoff != 1 and the kernel is vulnerable, this will trigger a warning and may fail to dump the interface information

Affected if The command fails, produces a warning in dmesg related to rtnetlink/nla_put_s32, or returns incomplete output for the macvlan interface

You are affected if your kernel version is in the affected ranges AND you have a macvlan interface with bc_cutoff set to a value other than the default of 1, causing 'ip -d link show' to fail or warn when dumping that interface.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Upgrade available Upgrade to 6.6.141 / 6.12.91 / 6.18.33 or later

Fixed in 6.6.1416.12.916.18.33

Vendor patch git.kernel.org →

Interim mitigation

Apply the kernel patch that adds nla_total_size(4) to macvlan_get_size() to properly reserve space for the IFLA_MACVLAN_BC_CUTOFF attribute, or upgrade to a kernel version containing the fix.

Recommended fix High confidence

Upgrade to kernel >= 6.6.141, >= 6.12.91, >= 6.18.33, or >= 7.0.10 depending on your current branch

Identify the currently running kernel version using 'uname -r'
Determine which version branch your kernel comes from (e.g., 6.6.x, 6.7.x, 6.13.x, 6.19.x)
Upgrade to a kernel version greater than or equal to the fixed release for your branch: 6.6.141, 6.12.91, 6.18.33, or 7.0.10
On Debian/Ubuntu: run 'sudo apt-get update && sudo apt-get upgrade' or install specific kernel package
On RHEL/CentOS: run 'sudo yum update kernel'
On Fedora: run 'sudo dnf upgrade kernel'
Reboot the system to load the new kernel
Verify the fix is applied by running: ip link add macvlan0 link lo type macvlan mode bridge && ip link set macvlan0 type macvlan bc_cutoff 0 && ip -d link show macvlan0

Caveat Kernel upgrades may require rebooting services; ensure compatibility with system dependencies and signed kernel modules

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory

Consultation1.0 h
Implementation2.0 h
Testing3.0 h
Review / QA1.0 h

7.0 hours of engineering $1,190

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References

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53013 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2026-53013?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

A fix existsUpgrade to 6.6.141 / 6.12.91 or later

Severity 5.5 Medium

Exploit likelihood EPSS, next 30 days 0.1%

Affects: Linux Kernel

Remediation

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Fix this in Linux Kernel 7 hrs · Low

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Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

Check your environment

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References