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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-07-14

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.

Affected products

Linux kernel: from 6.4 before 6.6.141; from 6.7 before 6.12.91; from 6.13 before 6.18.33; from 6.19 before 7.0.10 — fixed in 6.12.91, 6.18.33, 6.6.141, 7.0.10

How to fix

Upgrade to a fixed version: Linux kernel 6.12.91, 6.18.33, 6.6.141, 7.0.10. Check the vendor advisory for mitigations.

References

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