How severe is CVE-2021-40343?

CVE-2021-40343 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-40343 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40343?

CVE-2021-40343 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-40343?

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-2021-40343 published?

CVE-2021-40343 was published on 2021-10-26 and last updated on 2026-06-17.

CVE-2021-40343

CVE-2021-40343 is a high-severity vulnerability in Nagios Nagios Xi with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-732.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 7.2
EPSS exploit prediction: 1% (47th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-732
Affected product: Nagios Nagios Xi
Published: 2021-10-26
Last modified: 2026-06-17

Description

An issue was discovered in Nagios XI 5.8.5. Insecure file permissions on the nagios_unbundler.py file allow the nagios user to elevate their privileges to the root user.

Frequently asked questions

What is CVE-2021-40343?: An issue was discovered in Nagios XI 5.8.5. Insecure file permissions on the nagios_unbundler.py file allow the nagios user to elevate their privileges to the root user.
How severe is CVE-2021-40343?: CVE-2021-40343 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-40343 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40343?: CVE-2021-40343 affects Nagios Nagios Xi. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-40343?: 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-2021-40343 published?: CVE-2021-40343 was published on 2021-10-26 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nagios:nagios_xi:5.8.5:*:*:*:*:*:*:*

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