---
id: CVE-2026-98303
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup

  When the forward output route cannot be used in icmp_route_lookup(),
  it enters the "reverse path" …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup

  When the forward output route cannot be used in icmp_route_lookup(),
  it enters the "reverse path" …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    06083cea4a3b95f5ebc85312f97d7086e6c9e782
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    83aa83f81a8fec30ff5372dee60b2f0561bcb2ca
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    cac69c50716c712ef0114837c9427da66066124c
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    1af2d87964d87ba7626d96928d68c09158b5a223
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    fda3000147dc96c75ba162f680bec0a9fecf3037
  - >-
    Linux >= 8b7817f3a959ed99d7443afc12f78a7e1fcc2063 <
    2998147b59c9df0a51477c7a6b3d1f0ba3127dd4
  - Linux 2.6.25
published: '2026-10-06'
updated: '2026-10-06'
sourceUpdated: '2026-10-06T09:18:21.370'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98303'
references:
  - url: 'https://git.kernel.org/stable/c/06083cea4a3b95f5ebc85312f97d7086e6c9e782'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1af2d87964d87ba7626d96928d68c09158b5a223'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2998147b59c9df0a51477c7a6b3d1f0ba3127dd4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/83aa83f81a8fec30ff5372dee60b2f0561bcb2ca'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/cac69c50716c712ef0114837c9427da66066124c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fda3000147dc96c75ba162f680bec0a9fecf3037'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-06T08:50:17.412Z'
---

## Overview

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

ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup

When the forward output route cannot be used in icmp_route_lookup(),
it enters the "reverse path" and calls ip_route_input() on fl4_dec.daddr,
the original packet's source address.

ip_route_input() only returns an error for truly invalid packets. For
unreachable addresses it will succeed and return an input route whose
dst.output is set to ip_rt_bug(). The existing check only rejects
RTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned
and later used for output, syzkaller triggering a WARN_ON_ONCE()
in ip_rt_bug() as bellow:

 ------------[ cut here ]------------
 WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20
 RIP: 0010:ip_rt_bug+0x14/0x20
 Call Trace:
  ip_push_pending_frames+0xfa/0x100
  __icmp_send+0x905/0xf10
  ip_options_compile+0xc0/0xd0
  ip_rcv_finish_core+0x321/0xae0
  ip_rcv+0x1de/0x260
  __netif_receive_skb_one_core+0x11a/0x130
  netif_receive_skb+0x7b/0x260
  tun_get_user+0x11bf/0x1c10
 ------------[ cut here ]------------

Reject input route that is RTN_UNREACHABLE to fix it. The net warning
is only printed for RTN_LOCAL, as RTN_UNREACHABLE is not the result of
a race condition.

## Remediation

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