Nagios flaws being used in attacks

CISA lists 4 flaws in Nagios products as being used in attacks, most recently on 18 Jan 2022.

What to do

1. Update every Nagios product you use.Install the updates Nagios offers, on every device, and restart when asked. Each flaw below has a fix or clear advice; that’s one of CISA’s conditions for listing it.
2. If someone looks after IT for you, send them this page.Many of these are in equipment you don’t see: routers, firewalls, servers, the office network. Ask them to confirm each one is fixed, or that you don’t use the product.
3. Check anything else in the lookup.Search any app, company or CVE. Not being on CISA’s list doesn’t mean safe: keep updating either way.

Every flaw, newest first

1. Being used in attacksAdded by CISA on 18 Jan 2022
   Nagios XI
   CVE-2021-25298Nagios XI OS Command Injection
   Nagios XI contains a vulnerability which can lead to OS command injection on the Nagios XI server.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
2. Being used in attacksAdded by CISA on 18 Jan 2022
   Nagios XI
   CVE-2021-25297Nagios XI OS Command Injection
   Nagios XI contains a vulnerability which can lead to OS command injection on the Nagios XI server.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
3. Being used in attacksAdded by CISA on 18 Jan 2022
   Nagios XI
   CVE-2021-25296Nagios XI OS Command Injection
   Nagios XI contains a vulnerability which can lead to OS command injection on the Nagios XI server.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD
4. Being used in attacksAdded by CISA on 3 Nov 2021
   Nagios XI
   CVE-2019-15949Nagios XI Remote Code Execution Vulnerability
   Nagios XI contains a remote code execution vulnerability in which a user can modify the check_plugin executable and insert malicious commands to execute as root.
   CISA’s required actionApply updates per vendor instructions.
   CVE recordNVD

From CISA’s Known Exploited Vulnerabilities catalog, updated 21 Oct 2026 (version 2026.10.21). CISA’s required actions are written for US government agencies. Nagios on CISA’s site.