How severe is CVE-2021-36366?

CVE-2021-36366 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-36366 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36366?

CVE-2021-36366 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-36366?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-36366 published?

CVE-2021-36366 was published on 2021-09-28 and last updated on 2026-06-17.

CVE-2021-36366

CVE-2021-36366 is a critical-severity vulnerability in Nagios Nagios Xi with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 4% (89th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Nagios Nagios Xi
Published: 2021-09-28
Last modified: 2026-06-17

Description

Nagios XI before 5.8.5 incorrectly allows manage_services.sh wildcards.

Frequently asked questions

What is CVE-2021-36366?: Nagios XI before 5.8.5 incorrectly allows manage_services.sh wildcards.
How severe is CVE-2021-36366?: CVE-2021-36366 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-36366 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36366?: CVE-2021-36366 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-36366?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-36366 published?: CVE-2021-36366 was published on 2021-09-28 and last updated on 2026-06-17.

References

Affected products (1)

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

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