What is CVE-2020-27991?

CVE-2020-27991 is a medium-severity vulnerability in Nagios Xi, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2020-11-16.

How severe is CVE-2020-27991?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Nagios Xi

CVE-2020-27991

Nagios XI before 5.7.5 is vulnerable to XSS in Account Information (Email field).

Vulnerability class: XSS (Cross-Site Scripting)

Published 2020-11-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.344 (98.4th percentile), scored 2026-09-30.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 98th percentile — 98.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.344 · newest: 0.344 · change: 0.000

Affected products

Nagios Xi

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

www.nagios.com/downloads/nagios-xi/change-log/ (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2020-27991?: CVE-2020-27991 is a medium-severity vulnerability in Nagios Xi, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2020-11-16.
How severe is CVE-2020-27991?: Medium severity. CVSS v3 base score is 5.4 out of 10.