---
id: CVE-2024-56647
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: Fix icmp host relookup triggering ip_rt_bug

  arp link failure may trigger ip_rt_bug while xfrm enabled, call trace is:

  WARNING: CPU: 0 PID: 0 at net/ipv4/route.c:…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: Fix icmp host relookup triggering ip_rt_bug

  arp link failure may trigger ip_rt_bug while xfrm enabled, call trace is:

  WARNING: CPU: 0 PID: 0 at net/ipv4/route.c:…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.25, < 6.12.5'
  - linux_kernel = 6.13
patched:
  - linux_kernel 6.12.5
published: '2024-12-27'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:17:08.380'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2024-56647'
references:
  - url: 'https://git.kernel.org/stable/c/9545011e7b2a8fc0cbd6e387a09f12cd41d7d82f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c44daa7e3c73229f7ac74985acb8c7fb909c4e0a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d50981aaaefc3b04490fbc8274d37881a2b1b112'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/da54b3039d436227deebbc202cefea63bd318a38'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-784472.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00223
epssPercentile: 0.12848
ingestedAt: '2026-10-15T03:30:12.774Z'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-10-01T20:00:32.629636Z'
---

## Overview

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

net: Fix icmp host relookup triggering ip_rt_bug

arp link failure may trigger ip_rt_bug while xfrm enabled, call trace is:

WARNING: CPU: 0 PID: 0 at net/ipv4/route.c:1241 ip_rt_bug+0x14/0x20
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.12.0-rc6-00077-g2e1b3cc9d7f7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:ip_rt_bug+0x14/0x20
Call Trace:
 <IRQ>
 ip_send_skb+0x14/0x40
 __icmp_send+0x42d/0x6a0
 ipv4_link_failure+0xe2/0x1d0
 arp_error_report+0x3c/0x50
 neigh_invalidate+0x8d/0x100
 neigh_timer_handler+0x2e1/0x330
 call_timer_fn+0x21/0x120
 __run_timer_base.part.0+0x1c9/0x270
 run_timer_softirq+0x4c/0x80
 handle_softirqs+0xac/0x280
 irq_exit_rcu+0x62/0x80
 sysvec_apic_timer_interrupt+0x77/0x90

The script below reproduces this scenario:
ip xfrm policy add src 0.0.0.0/0 dst 0.0.0.0/0 \
	dir out priority 0 ptype main flag localok icmp
ip l a veth1 type veth
ip a a 192.168.141.111/24 dev veth0
ip l s veth0 up
ping 192.168.141.155 -c 1

icmp_route_lookup() create input routes for locally generated packets
while xfrm relookup ICMP traffic.Then it will set input route
(dst->out = ip_rt_bug) to skb for DESTUNREACH.

For ICMP err triggered by locally generated packets, dst->dev of output
route is loopback. Generally, xfrm relookup verification is not required
on loopback interfaces (net.ipv4.conf.lo.disable_xfrm = 1).

Skip icmp relookup for locally generated packets to fix it.

## Affected

- `linux_kernel >= 2.6.25, < 6.12.5`
- `linux_kernel = 6.13`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.12.5`