---
id: CVE-2026-20040
title: "A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary commands as root on the underlying operating system of an affected device.\r\n\r\nThis vulnerability is due to insufficient…"
summary: "A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary commands as root on the underlying operating system of an affected device.\r\n\r\nThis vulnerability is due to insufficient…"
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
cwe:
  - CWE-78
vendor: cisco
product: ios_xr
affected:
  - ios_xr < 25.2.21
  - 'ios_xr >= 25.3.1, < 25.4.2'
patched:
  - ios_xr 25.4.2
published: '2026-03-11'
updated: '2026-07-01'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20040'
references:
  - url: >-
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-privesc-bF8D5U4W
    label: psirt@cisco.com
tags:
  - nvd
epss: 0.00172
epssPercentile: 0.05789
ingestedAt: '2026-07-01T16:42:14.726Z'
---

## Overview

A vulnerability in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to execute arbitrary commands as root on the underlying operating system of an affected device.

This vulnerability is due to insufficient validation of user arguments that are passed to specific CLI commands. An attacker with a low-privileged account could exploit this vulnerability by using crafted commands at the prompt. A successful exploit could allow the attacker to elevate privileges to root and execute arbitrary commands on the underlying operating system.

## Affected

- `ios_xr < 25.2.21`
- `ios_xr >= 25.3.1, < 25.4.2`

## Remediation

Upgrade past the affected range:

- `ios_xr 25.4.2`