What is CVE-2021-26023?

CVE-2021-26023 is a medium-severity vulnerability in Nagios Favorites, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-02-03.

How severe is CVE-2021-26023?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Nagios Favorites

CVE-2021-26023

The Favorites component before 1.0.2 for Nagios XI 5.8.0 is vulnerable to XSS.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-02-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.252 (97.9th percentile), scored 2026-09-29.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 98th percentile — 97.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.252 · newest: 0.252 · change: 0.000

Affected products

Nagios Favorites
Nagios Xi — versions 5.8.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

www.nagios.com/products/security/ (Vendor Advisory)

Frequently asked questions

What is CVE-2021-26023?: CVE-2021-26023 is a medium-severity vulnerability in Nagios Favorites, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-02-03.
How severe is CVE-2021-26023?: Medium severity. CVSS v3 base score is 6.1 out of 10.