CVE-2026-48550 Nagios Core / XI cmd.cgi Reflected XSS via NagFormId Parameter
An unauthenticated attacker can execute arbitrary JavaScript in an authenticated user's browser via a crafted link in Nagios Core or XI.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-48550?
CVE-2026-48550 is a medium-severity cross-site scripting vulnerability in Nagios Core, published on 12 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-48550?
How do I fix CVE-2026-48550?
Upgrade to a fixed version.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-48550 being exploited?
There is no known exploitation of CVE-2026-48550 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-48550, GHSA-hc96-98mh-7j3h, UBUNTU-CVE-2026-48550.