CVE-2021-47699: Nagios XI < 5.8.7 XSS in Audit Log via Send to NLS Form

Severity: medium (CVSS 5.4 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: 2025-10-30 · updated 2026-06-17
Weakness: CWE-79

Description

Nagios XI versions prior to 5.8.7 are vulnerable to cross-site scripting (XSS) via the Audit Log page’s Send to NLS form. Insufficient validation or escaping of user-supplied input may allow an attacker to inject and execute arbitrary script in the context of a victim's browser.

Affected products

Nagios XI: before 5.8.7 — fixed in 5.8.7

How to fix

Upgrade to a fixed version: Nagios XI 5.8.7. Check the vendor advisory for mitigations.

References

https://www.nagios.com/changelog/nagios-xi/
https://www.vulncheck.com/advisories/nagios-xi-xss-in-audit-log-via-send-to-nls-form

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