CVE-2026-23381 net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
A local attacker can cause a kernel crash by sending ICMPv6 packets to a bridge with neighbor suppression enabled while IPv6 is disabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23381?
CVE-2026-23381 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-476
Which versions are affected by CVE-2026-23381?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23381?
Apply the vendor's patch.
Is CVE-2026-23381 being exploited?
There is no known exploitation of CVE-2026-23381 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-80702, BELL-CVE-2026-23381, DEBIAN-CVE-2026-23381, GHSA-vm87-vmvc-9c38, ROOT-OS-DEBIAN-11-CVE-2026-23381, ROOT-OS-DEBIAN-12-CVE-2026-23381 and 4 more.