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CVE Record

CVE-2026-23381: net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can crash affected systems when a specific bridge networking configuration receives IPv6 Neighbor Discovery traffic while IPv6 was disabled at boot. The business impact is primarily availability, not data theft, based on the provided sources.

Executive priority

Prioritize patching for network infrastructure, virtualization hosts, appliances, and embedded systems using Linux bridge features. For ordinary servers without this bridge and IPv6-disabled configuration, urgency is lower but should remain in normal kernel maintenance.

Technical view

With ipv6.disable=1, nd_tbl is not initialized because inet6_init exits before ndisc_init. If bridge neigh_suppress is enabled and an ICMPv6 Neighbor Discovery packet reaches the bridge, br_do_suppress_nd dereferences ipv6_stub->nd_tbl as NULL, causing a kernel NULL pointer dereference.

Likely exposure

Exposure appears limited to affected Linux kernels using Linux bridge networking with IPv6 disabled at boot, bridge neighbor suppression enabled, and ICMPv6 Neighbor Discovery traffic reaching the bridge. Systems not using this configuration are less likely to be exposed based on the supplied description.

Exploitation context

The source bundle does not show CISA KEV listing or cited active exploitation. The trigger requires a particular runtime configuration and packet type reaching a bridge. Treat it as a denial-of-service risk until vendor advisories provide more detail.

Researcher notes

The key bug is runtime IPv6 disablement bypassing nd_tbl initialization while compile-time IPv6 checks still allowed bridge ND suppression paths. The listed fix changes callers to use ipv6_mod_enabled, effectively disabling NS/NA suppression when IPv6 is disabled.

Mitigation direction

  • Apply Linux kernel or distribution updates containing the referenced stable fixes.
  • Review Siemens advisories if Siemens products are in scope.
  • Avoid enabling bridge neighbor suppression on IPv6-disabled hosts until patched.
  • Check vendor guidance for exact fixed package versions.
  • Prioritize exposed bridge hosts over general Linux endpoints.

Validation and detection

  • Inventory Linux hosts running affected kernel versions or vendor builds.
  • Check whether systems boot with ipv6.disable=1.
  • Identify Linux bridges with neigh_suppress enabled.
  • Confirm fixed stable commits or vendor patches are installed.
  • Review kernel logs for related NULL pointer dereference crashes.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
11Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30, ed842faeb2bd49256f00485402f3113205f91d30unaffected
LinuxLinux4.15, 0, 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77, 6.18.17, 6.19.7, 7.0affected
Weakness

CWE details

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