CVE-2026-23381

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/a9d712ccfeef737c0e700a4b5b98f310e07b6b60
• https://git.kernel.org/stable/c/a5c56e65b685360dd3f2278aeff8c21061feb665
• https://git.kernel.org/stable/c/7a894eb5de246d79f13105c55a67381039a24d44
• https://git.kernel.org/stable/c/a12cdaa3375f0bd3c8f4e564be7c143529abfe5b
• https://git.kernel.org/stable/c/aa73deb3b6b730ec280d45b3f423bfa9e17bc122
• https://git.kernel.org/stable/c/33dec6f10777d5a8f71c0a200f690da5ae3c2e55
• https://git.kernel.org/stable/c/20ef5c25422f97dd09d751e5ae6c18406cdc78e6
• https://git.kernel.org/stable/c/e5e890630533bdc15b26a34bb8e7ef539bdf1322

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