---
id: "CVE-2026-99073"
kind: "vulnerability"
aliases: ["CVE-2026-99073"]
title: "Linux kernel: IPv4 route dump can crash when nexthop group shrinks"
severity: "unknown"
cvss: null
epss: 0.00209
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ipv4", "linux-kernel", "routers", "runtime"]
not_affected_if: ["no-nexthop-groups"]
published_at: "2026-10-23T13:17:31+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99073", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-99073", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: IPv4 route dump can crash when nexthop group shrinks

A race in the Linux kernel's IPv4 FIB dump code lets a route dump run while a nexthop group is being replaced with one that has fewer paths. The dump then dereferences a null pointer, which can crash the kernel.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `uname -r` and compare against the fixed kernel builds listed in the NVD entry.
- unknown

## Fix

- Update the Linux kernel to a release that includes the upstream commit resolving CVE-2026-99073 (the fixed version is not stated in the sources).
- unknown

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99073
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-99073

## From the sources

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

ipv4: stop exception dump when nexthop group shrinks

Commit 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU
protection") allowed IPv4 FIB dumps to run concurrently with nexthop
replacement.

fib_dump_info_fnhe() uses fib_info_num_path() as the loop bound,
then fib_info_nhc() independently reloads nh->nh_grp. If
RTM_NEWNEXTHOP replaces a group with fewer paths between those loads,
fib_info_nhc() returns NULL and the dump dereferences it through
nhc_flags.

Stop the walk when the indexed path is absent. Nexthop groups are
dense, so the current snapshot has no later path.

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