CVE-2021-43033

Name: CVE-2021-43033
Creator: NVD / NIST
Published: 2021-12-06T04:15:07.093+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 5.99%

Last modified Jun 17, 2026

CVE-2021-43033 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. Multiple functions in the bpserverd daemon were vulnerable to arbitrary remote code execution as root. EPSS estimates a 5.99% chance of exploitation in the next 30 days.

Description

An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. Multiple functions in the bpserverd daemon were vulnerable to arbitrary remote code execution as root. The vulnerability was caused by untrusted input (received by the server) being passed to system calls.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

5.99%

92.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-78

Affected Software

Vendor	Product	Versions
Kaseya	Unitrends Backup	>= 10.0, < 10.5.5

References

https://helpdesk.kaseya.com/hc/en-gb/articles/4412762258961Vendor Advisory
https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-1Exploit, Third Party Advisory
https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-2Exploit, Third Party Advisory
https://helpdesk.kaseya.com/hc/en-gb/articles/4412762258961Vendor Advisory
https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-1Exploit, Third Party Advisory
https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-2Exploit, Third Party Advisory

Timeline

Published: Dec 6, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43033?

How severe is CVE-2021-43033?

CVE-2021-43033 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 5.99% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43033?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43033?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST