CVE-2021-43039

Name: CVE-2021-43039
Creator: NVD / NIST
Published: 2021-12-06T04:15:07.397+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.22%

Last modified Jun 17, 2026

CVE-2021-43039 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The Samba file sharing service allowed anonymous read/write access.. EPSS estimates a 1.22% chance of exploitation in the next 30 days.

Description

An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The Samba file sharing service allowed anonymous read/write access.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.22%

64.7th percentile

Probability of exploitation in the next 30 days. Learn more

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-2021-43039?

An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The Samba file sharing service allowed anonymous read/write access.

How severe is CVE-2021-43039?

CVE-2021-43039 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.22% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43039?

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-2021-43039?

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

Scan your code now

Source: NVD / NIST