How severe is CVE-2021-25299?

CVE-2021-25299 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-25299 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 98% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25299?

CVE-2021-25299 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-25299?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-25299 published?

CVE-2021-25299 was published on 2021-02-15 and last updated on 2026-07-05.

CVE-2021-25299

CVE-2021-25299 is a medium-severity vulnerability in Nagios Nagios Xi with a CVSS 3.x base score of 6.1. Its EPSS exploit-prediction score of 98% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 98% (100th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Nagios Nagios Xi
Published: 2021-02-15
Last modified: 2026-07-05

Description

Nagios XI version xi-5.7.5 is affected by cross-site scripting (XSS). The vulnerability exists in the file /usr/local/nagiosxi/html/admin/sshterm.php due to improper sanitization of user-controlled input. A maliciously crafted URL, when clicked by an admin user, can be used to steal his/her session cookies or it can be chained with the previous bugs to get one-click remote command execution (RCE) on the Nagios XI server.

Frequently asked questions

What is CVE-2021-25299?: Nagios XI version xi-5.7.5 is affected by cross-site scripting (XSS). The vulnerability exists in the file /usr/local/nagiosxi/html/admin/sshterm.php due to improper sanitization of user-controlled input. A maliciously crafted URL, when clicked by an admin user, can be used to steal his/her session cookies or it can be chained with the previous bugs to get one-click remote command execution (RCE) on the Nagios XI server.
How severe is CVE-2021-25299?: CVE-2021-25299 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-25299 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 98% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-25299?: CVE-2021-25299 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-25299?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-25299 published?: CVE-2021-25299 was published on 2021-02-15 and last updated on 2026-07-05.

References

Affected products (1)

cpe:2.3:a:nagios:nagios_xi:5.7.5:*:*:*:*:*:*:*

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