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Actively exploited

CVE-2021-25296 Nagios XI OS Command Injection

Nagios XI contains a vulnerability which can lead to OS command injection on the Nagios XI server.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch urgentlyCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 18 Jan 2022.
  • Rated High severity (CVSS 8.8, scored by CISA).
  • It has been in the catalogue for 1,753 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

Nagios XI version xi-5.7.5 is affected by OS command injection. The vulnerability exists in the file /usr/local/nagiosxi/html/includes/configwizards/windowswmi/windowswmi.inc.php due to improper sanitization of authenticated user-controlled input by a single HTTP request, which can lead to OS command injection on the Nagios XI server.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Nagios XI. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 1 Feb 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Nagios Flaws

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CVE-2021-25297Nagios XI OS Command InjectionAdded 18 Jan 2022CVE-2021-25298Nagios XI OS Command InjectionAdded 18 Jan 2022CVE-2019-15949Nagios XI Remote Code Execution VulnerabilityAdded 3 Nov 2021

All 4 exploited Nagios vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-25296
  3. CVE record: CVE-2021-25296
  4. FIRST EPSS
  5. assets.nagios.com/downloads/nagiosxi/versions.php
  6. github.com/fs0c-sh/nagios-xi-5.7.5-bugs/blob/main/README.md
  7. packetstormsecurity.com/files/161561/Nagios-XI-5.7.5-Remote-Code-Execution.html
  8. packetstormsecurity.com/files/170924/Nagios-XI-5.7.5-Remote-Code-Execution.html
  9. fastly.com/blog/anatomy-of-a-command-injection-cve-2021-25296-7-8-with-metasploit-module-and