---
id: CVE-2025-20340
title: >-
  A vulnerability in the Address Resolution Protocol (ARP) implementation of
  Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to
  trigger a broadcast storm, leading to a denial of service (DoS) condition on
  an affecte…
summary: >-
  A vulnerability in the Address Resolution Protocol (ARP) implementation of
  Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to
  trigger a broadcast storm, leading to a denial of service (DoS) condition on
  an affecte…
severity: high
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'
cwe:
  - CWE-400
published: '2025-09-10'
updated: '2026-09-26'
sourceUpdated: '2026-09-26T00:10:00.127'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-20340'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-arp-storm-EjUU55yM
    label: psirt@cisco.com
tags:
  - nvd
epss: 0.0061
epssPercentile: 0.46999
ingestedAt: '2026-09-26T00:22:39.914Z'
---

## Overview

A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. 

This vulnerability is due to how Cisco IOS XR Software processes a high, sustained rate of ARP traffic hitting the management interface. Under certain conditions, an attacker could exploit this vulnerability by sending an excessive amount of traffic to the management interface of an affected device, overwhelming its ARP processing capabilities. A successful exploit could result in degraded device performance, loss of management connectivity, and complete unresponsiveness of the system, leading to a DoS condition.

## Remediation

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