CVE-2026-23381

MediumCVSS 5.5/10Last modified Nov 10, 2026

Description

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

net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled

When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never initialized because inet6_init() exits before ndisc_init() is called which initializes it. Then, if neigh_suppress is enabled and an ICMPv6 Neighbor Discovery packet reaches the bridge, br_do_suppress_nd() will dereference ipv6_stub->nd_tbl which is NULL, passing it to neigh_lookup(). This causes a kernel NULL pointer dereference.

BUG: kernel NULL pointer dereference, address: 0000000000000268 Oops: 0000 [#1] PREEMPT SMP NOPTI [...] RIP: 0010:neigh_lookup+0x16/0xe0 [...] Call Trace: <IRQ> ? neigh_lookup+0x16/0xe0 br_do_suppress_nd+0x160/0x290 [bridge] br_handle_frame_finish+0x500/0x620 [bridge] br_handle_frame+0x353/0x440 [bridge] __netif_receive_skb_core.constprop.0+0x298/0x1110 __netif_receive_skb_one_core+0x3d/0xa0 process_backlog+0xa0/0x140 __napi_poll+0x2c/0x170 net_rx_action+0x2c4/0x3a0 handle_softirqs+0xd0/0x270 do_softirq+0x3f/0x60

Fix this by replacing IS_ENABLED(IPV6) call with ipv6_mod_enabled() in the callers. This is in essence disabling NS/NA suppression when IPv6 is disabled.

Metrics

CVSS 3.1 5.5/10CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-476

Affected software

VendorProductVersions
LinuxLinux>= ed842faeb2bd49256f00485402f3113205f91d30, < a9d712ccfeef737c0e700a4b5b98f310e07b6b60; >= ed842faeb2bd49256f00485402f3113205f91d30, < a5c56e65b685360dd3f2278aeff8c21061feb665; >= ed842faeb2bd49256f00485402f3113205f91d30, < 7a894eb5de246d79f13105c55a67381039a24d44; >= ed842faeb2bd49256f00485402f3113205f91d30, < a12cdaa3375f0bd3c8f4e564be7c143529abfe5b; >= ed842faeb2bd49256f00485402f3113205f91d30, < aa73deb3b6b730ec280d45b3f423bfa9e17bc122; >= ed842faeb2bd49256f00485402f3113205f91d30, < 33dec6f10777d5a8f71c0a200f690da5ae3c2e55; >= ed842faeb2bd49256f00485402f3113205f91d30, < 20ef5c25422f97dd09d751e5ae6c18406cdc78e6; >= ed842faeb2bd49256f00485402f3113205f91d30, < e5e890630533bdc15b26a34bb8e7ef539bdf1322
LinuxLinux4.15
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.6, < *
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.5, < *
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.7, < *
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.6, < *
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.5, < *
SiemensSIMATIC S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.7, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.6, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.5, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.7, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.6, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.5, < *
SiemensSIMATIC S7-1500 CPU 1518F-4 PN/DP MFP>= V3.1.7, < *
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystem< *
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.6, < *
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.5, < *
SiemensSIPLUS S7-1500 CPU 1518-4 PN/DP MFP>= V3.1.7, < *

References

Timeline

Published
Mar 25, 2026
Last modified
Nov 10, 2026
NVD status
Modified

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CVE-2026-23381: Medium severity, CVSS 5.5 | Vulnix