How severe is CVE-2021-43040?

CVE-2021-43040 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43040 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43040?

CVE-2021-43040 affects Kaseya Unitrends Backup. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43040?

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-2021-43040 published?

CVE-2021-43040 was published on 2021-12-06 and last updated on 2026-06-17.

CVE-2021-43040

CVE-2021-43040 is a high-severity vulnerability in Kaseya Unitrends Backup with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 2% (75th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Kaseya Unitrends Backup
Published: 2021-12-06
Last modified: 2026-06-17

Description

An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The privileged vaultServer could be leveraged to create arbitrary writable files, leading to privilege escalation.

Frequently asked questions

What is CVE-2021-43040?: An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The privileged vaultServer could be leveraged to create arbitrary writable files, leading to privilege escalation.
How severe is CVE-2021-43040?: CVE-2021-43040 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43040 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43040?: CVE-2021-43040 affects Kaseya Unitrends Backup. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43040?: 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-2021-43040 published?: CVE-2021-43040 was published on 2021-12-06 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:kaseya:unitrends_backup:*:*:*:*:*:*:*:*

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