CVE-2026-43100

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

bridge: guard local VLAN-0 FDB helpers against NULL vlan group

When CONFIG_BRIDGE_VLAN_FILTERING is not set, br_vlan_group() and

nbp_vlan_group() return NULL (br_private.h stub definitions). The

BR_BOOLOPT_FDB_LOCAL_VLAN_0 toggle code is compiled unconditionally and

reaches br_fdb_delete_locals_per_vlan_port() and

br_fdb_insert_locals_per_vlan_port(), where the NULL vlan group pointer

is dereferenced via list_for_each_entry(v, &vg->vlan_list, vlist).

The observed crash is in the delete path, triggered when creating a

bridge with IFLA_BR_MULTI_BOOLOPT containing BR_BOOLOPT_FDB_LOCAL_VLAN_0

via RTM_NEWLINK. The insert helper has the same bug pattern.

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000056: 0000 [#1] KASAN NOPTI

KASAN: null-ptr-deref in range [0x00000000000002b0-0x00000000000002b7]

RIP: 0010:br_fdb_delete_locals_per_vlan+0x2b9/0x310

Call Trace:

br_fdb_toggle_lo

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References