CVE-2026-53013

Summary

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 Software

Weaknesses

References

• https://git.kernel.org/stable/c/4979252758387b338ca968ba7e0515b0ae2257e3
• https://git.kernel.org/stable/c/77ecfa4e27f282d224215895ddfbeb916fc75e24
• https://git.kernel.org/stable/c/b6b7154e9f5d75b608ceb2d05b376de8c638c40e
• https://git.kernel.org/stable/c/1c004f14ccdc11585625c168bb9a7c5e1b8afb0c
• https://git.kernel.org/stable/c/fa92a77b0ed4d5f11a71665a232ac5a54a4b055d

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