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Linux Kernel CVE-2026-43100

| EUVDEUVD-2026-27610 MEDIUM
NULL Pointer Dereference (CWE-476)
2026-05-06 Linux GHSA-r5qw-5m8q-6774
Canonical Denial Of Service Null Pointer Dereference Linux Red Hat Suse
5.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
SUSE
MEDIUM
qualitative
Red Hat
5.5 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

4
Analysis Generated
May 11, 2026 - 17:37 vuln.today
CVSS changed
May 11, 2026 - 17:37 NVD
5.5 (MEDIUM)
Patch available
May 06, 2026 - 11:31 EUVD
CVE Published
May 06, 2026 - 07:40 nvd
MEDIUM 5.5

DescriptionCVE.org

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_local_vlan_0+0x452/0x4c0 br_toggle_fdb_local_vlan_0+0x31/0x80 net/bridge/br.c:276 br_boolopt_toggle net/bridge/br.c:313 br_boolopt_multi_toggle net/bridge/br.c:364 br_changelink net/bridge/br_netlink.c:1542 br_dev_newlink net/bridge/br_netlink.c:1575

Add NULL checks for the vlan group pointer in both helpers, returning early when there are no VLANs to iterate. This matches the existing pattern used by other bridge FDB functions such as br_fdb_add() and br_fdb_delete().

AnalysisAI

Null pointer dereference in Linux kernel bridge VLAN filtering code allows local authenticated attackers to trigger a denial of service via a crafted RTM_NEWLINK netlink message with BR_BOOLOPT_FDB_LOCAL_VLAN_0 flag when CONFIG_BRIDGE_VLAN_FILTERING is disabled. The vulnerability occurs because br_fdb_delete_locals_per_vlan_port() and br_fdb_insert_locals_per_vlan_port() dereference a NULL vlan group pointer without validation, causing a kernel panic. No public exploit code identified at time of analysis.

Technical ContextAI

The Linux kernel bridge module implements VLAN filtering via the br_vlan_group() function, which returns NULL when CONFIG_BRIDGE_VLAN_FILTERING is not compiled in (stub definition in br_private.h). However, the BR_BOOLOPT_FDB_LOCAL_VLAN_0 toggle functionality is compiled unconditionally and attempts to iterate over the vlan group using list_for_each_entry(v, &vg->vlan_list, vlist) without checking if vg is NULL. This is a classic NULL pointer dereference (CWE-476) triggered when netlink RTM_NEWLINK messages create a bridge with IFLA_BR_MULTI_BOOLOPT containing the FDB local VLAN 0 flag. The bug pattern exists in both the delete and insert helper functions due to asymmetric guard coverage-other bridge FDB functions like br_fdb_add() and br_fdb_delete() properly check for NULL vlan groups before proceeding.

RemediationAI

Apply vendor-released patch from stable kernel branches: Linux 6.19.14, 6.18.24, or 7.0 or later. The fix adds NULL pointer checks in br_fdb_delete_locals_per_vlan_port() and br_fdb_insert_locals_per_vlan_port() to return early if vg is NULL, matching existing patterns in br_fdb_add() and br_fdb_delete(). Systems unable to immediately patch should restrict unprivileged user access to netlink socket creation via seccomp/selinux policies or disable bridge module if not required (rmmod br). For systems with CONFIG_BRIDGE_VLAN_FILTERING enabled (default in most distributions), exploitation is not possible, making this primarily a risk to minimal embedded/custom kernel builds. Patches are available from kernel.org stable branches: https://git.kernel.org/stable/c/fb612d436ff0317659e45a91c25fd7d9516f5b1b

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed

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CVE-2026-43100 vulnerability details – vuln.today
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