---
id: CVE-2024-56751
title: 'ipv6: release nexthop on device removal'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv6: release nexthop on device removal

  The CI is hitting some aperiodic hangup at device removal time in the
  pmtu.sh self-test:

  unregister_netdevice: waiting for vet…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    77aa9855a878fb43f547ddfbda3127a1e88ad31a
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    b2f26a27ea3f72f75d18330f76f5d1007c791848
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    43e25adc80269f917d2a195f0d59f74cdd182955
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    a3c3f8a4d025acc8c857246ec2b812c59102487a
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    0e4c6faaef8a24b762a24ffb767280e263ef8e10
  - >-
    Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 <
    eb02688c5c45c3e7af7e71f036a7144f5639cbfe
  - Linux 5.3
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:32:24.098521Z'
published: '2024-12-29'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T20:41:37.543Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2024-56751'
references:
  - url: 'https://git.kernel.org/stable/c/77aa9855a878fb43f547ddfbda3127a1e88ad31a'
  - url: 'https://git.kernel.org/stable/c/b2f26a27ea3f72f75d18330f76f5d1007c791848'
  - url: 'https://git.kernel.org/stable/c/43e25adc80269f917d2a195f0d59f74cdd182955'
  - url: 'https://git.kernel.org/stable/c/a3c3f8a4d025acc8c857246ec2b812c59102487a'
  - url: 'https://git.kernel.org/stable/c/0e4c6faaef8a24b762a24ffb767280e263ef8e10'
  - url: 'https://git.kernel.org/stable/c/eb02688c5c45c3e7af7e71f036a7144f5639cbfe'
tags:
  - cve.org
epss: 0.00219
epssPercentile: 0.12484
ingestedAt: '2026-11-05T22:38:31.843Z'
---

## Overview

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

ipv6: release nexthop on device removal

The CI is hitting some aperiodic hangup at device removal time in the
pmtu.sh self-test:

unregister_netdevice: waiting for veth_A-R1 to become free. Usage count = 6
ref_tracker: veth_A-R1@ffff888013df15d8 has 1/5 users at
	dst_init+0x84/0x4a0
	dst_alloc+0x97/0x150
	ip6_dst_alloc+0x23/0x90
	ip6_rt_pcpu_alloc+0x1e6/0x520
	ip6_pol_route+0x56f/0x840
	fib6_rule_lookup+0x334/0x630
	ip6_route_output_flags+0x259/0x480
	ip6_dst_lookup_tail.constprop.0+0x5c2/0x940
	ip6_dst_lookup_flow+0x88/0x190
	udp_tunnel6_dst_lookup+0x2a7/0x4c0
	vxlan_xmit_one+0xbde/0x4a50 [vxlan]
	vxlan_xmit+0x9ad/0xf20 [vxlan]
	dev_hard_start_xmit+0x10e/0x360
	__dev_queue_xmit+0xf95/0x18c0
	arp_solicit+0x4a2/0xe00
	neigh_probe+0xaa/0xf0

While the first suspect is the dst_cache, explicitly tracking the dst
owing the last device reference via probes proved such dst is held by
the nexthop in the originating fib6_info.

Similar to commit f5b51fe804ec ("ipv6: route: purge exception on
removal"), we need to explicitly release the originating fib info when
disconnecting a to-be-removed device from a live ipv6 dst: move the
fib6_info cleanup into ip6_dst_ifdown().

Tested running:

./pmtu.sh cleanup_ipv6_exception

in a tight loop for more than 400 iterations with no spat, running an
unpatched kernel  I observed a splat every ~10 iterations.

## Affected

- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 77aa9855a878fb43f547ddfbda3127a1e88ad31a`
- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < b2f26a27ea3f72f75d18330f76f5d1007c791848`
- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 43e25adc80269f917d2a195f0d59f74cdd182955`
- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < a3c3f8a4d025acc8c857246ec2b812c59102487a`
- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < 0e4c6faaef8a24b762a24ffb767280e263ef8e10`
- `Linux >= f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 < eb02688c5c45c3e7af7e71f036a7144f5639cbfe`
- `Linux 5.3`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.