Vulnerability · Published Aug 12, 2026 · Assigned by VulnCheck

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

Medium 6.1

In plain English

A medium-severity cross-site scripting in Nagios Core from Nagios Enterprises, LLC.. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.4%top 61.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	nagios4	4.4.6-4+deb12u2	DEBIAN-CVE-2026-48550
Debian:13	nagios4	4.4.6-4.1+deb13u2	DEBIAN-CVE-2026-48550
Debian:14	nagios4	4.5.14+ds-1	DEBIAN-CVE-2026-48550
Ubuntu:22.04:LTS	nagios4	no fix listed	UBUNTU-CVE-2026-48550
Ubuntu:24.04:LTS	nagios4	no fix listed	UBUNTU-CVE-2026-48550
Ubuntu:26.04:LTS	nagios4	no fix listed	UBUNTU-CVE-2026-48550
Ubuntu:26.10	nagios4	no fix listed	UBUNTU-CVE-2026-48550

Affected products (as reported)

Vendor	Product	Versions
Nagios Enterprises, LLC.	Nagios Core	0 – before 4.5.14
Nagios Enterprises, LLC.	Nagios XI	0 – before 2026R1.7

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

Security Disclosures vendor-advisory, patch
Changelog release-notes
https://www.vulncheck.com/advisories/nagios-core-xi-cmd-cgi-reflected-xss-via-nagformid-parameter third-party-advisory