What’s Vulnerable › Vulnerabilities

CVE-2026-48550: Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-09-08
• Weakness: CWE-79

Description

Nagios Core before 4.5.14 and Nagios XI before 2026R1.7 are vulnerable to reflected cross-site scripting in cmd.cgi via the NagFormId parameter. An unauthenticated remote attacker can craft a malicious link that, when followed by an authenticated user, executes arbitrary JavaScript in the victim's browser.

Affected products

• Nagios Enterprises, LLC. Nagios Core: before 4.5.14 — fixed in 4.5.14
• Nagios Enterprises, LLC. Nagios XI: before 2026R1.7 — fixed in 2026R1.7

How to fix

Upgrade to a fixed version: Nagios Enterprises, LLC. Nagios Core 4.5.14; Nagios Enterprises, LLC. Nagios XI 2026R1.7. Check the vendor advisory for mitigations.

References

• https://github.com/NagiosEnterprises/nagioscore/blob/master/Changelog
• https://www.nagios.com/security-disclosures/nagios-core/
• https://www.vulncheck.com/advisories/nagios-core-xi-cmd-cgi-reflected-xss-via-nagformid-parameter

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