How severe is CVE-2021-3277?

CVE-2021-3277 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-3277 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 55% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3277?

CVE-2021-3277 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3277?

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

When was CVE-2021-3277 published?

CVE-2021-3277 was published on 2021-06-07 and last updated on 2026-06-17.

CVE-2021-3277

CVE-2021-3277 is a high-severity vulnerability in Nagios Nagios Xi with a CVSS 3.x base score of 7.2. Its EPSS exploit-prediction score of 55% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-434.

Key facts

Severity: High (CVSS 3.x base score 7.2)
CVSS v2: 6.5
EPSS exploit prediction: 55% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Nagios Nagios Xi
Published: 2021-06-07
Last modified: 2026-06-17

Description

Nagios XI 5.7.5 and earlier allows authenticated admins to upload arbitrary files due to improper validation of the rename functionality in custom-includes component, which leads to remote code execution by uploading php files.

Frequently asked questions

What is CVE-2021-3277?: Nagios XI 5.7.5 and earlier allows authenticated admins to upload arbitrary files due to improper validation of the rename functionality in custom-includes component, which leads to remote code execution by uploading php files.
How severe is CVE-2021-3277?: CVE-2021-3277 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-3277 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 55% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3277?: CVE-2021-3277 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3277?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3277 published?: CVE-2021-3277 was published on 2021-06-07 and last updated on 2026-06-17.

References

https://asaf.me/2021/01/21/nagios-xi-5-7-5-remote-code-execution/

Affected products (1)

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

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