CVE-2026-53013 Linux CVE debrief

Who should care

Linux kernel maintainers and users who rely on macvlan for network interface management should be aware of this vulnerability. System administrators and security teams should verify their Linux kernel versions and ensure they are running a patched version to prevent potential issues with network interface dumping.

Technical summary

The macvlan_get_size() function in the Linux kernel does not account for the IFLA_MACVLAN_BC_CUTOFF attribute, leading to a potential -EMSGSIZE error when dumping network interface information. This issue arises when the netlink skb runs out of space due to the conditional inclusion of IFLA_MACVLAN_BC_CUTOFF in macvlan_fill_info(). The vulnerability can be reproduced by adding a macvlan interface, setting its bc_cutoff to 0, and then attempting to dump the interface information.

Defensive priority

Medium priority should be given to patching this vulnerability, as it could cause issues with network interface management and potentially lead to errors when dumping interface information. System administrators and security teams should verify their Linux kernel versions and ensure they are running a patched version to prevent potential issues with network interface dumping. This vulnerability 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 bug 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. 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 macvlan_get_size() function in the Linux kernel does not account for the IFLA_MACVLAN_BC_CUTOFF attribute, leading to a potential -EMSGSIZE error when dumping network interface information. This issue arises when the netlink skb runs out of space due to the conditional inclusion of IFLA_MACVLAN_BC_CUTOFF in macvlan_fill_info(). The vulnerability can be reproduced by adding a macvlan interface, setting its bc_cutoff to 0, and then attempting to dump the interface information. whoShouldCare: Linux kernel maintainers and users who rely on macvlan for network interface management should be aware of this vulnerability. System administrators and security teams should verify their Linux kernel versions and ensure they are running a patched version to prevent potential issues with network interface dumping. technicalSummary: The macvlan_get_size() function in the Linux kernel does not account for the IFLA_MACVLAN_BC_CUTOFF attribute, leading to a potential -EMSGSIZE error when dumping network interface information. This issue arises when the netlink skb runs out of space due to the conditional inclusion of IFLA_MACVLAN_BC_C

Recommended defensive actions

• Verify Linux kernel version and update to a patched version if necessary
• Review network interface configurations for macvlan and ensure bc_cutoff is set appropriately
• Monitor for potential errors when dumping network interface information
• Perform vulnerability assessment to identify potential exposure
• Implement compensating controls for exposed systems
• Track exceptions and retest remediated assets

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. Further analysis of the Linux kernel source code and testing may be necessary to fully understand the impact of this vulnerability. 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. Linux kernel maintainers should verify their kernel versions and ensure they are running a patched version to prevent potential issues with network interface dumping.

Official resources