How severe is CVE-2021-43033?

CVE-2021-43033 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43033 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43033?

CVE-2021-43033 affects Kaseya Unitrends Backup. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43033?

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

When was CVE-2021-43033 published?

CVE-2021-43033 was published on 2021-12-06 and last updated on 2026-06-17.

CVE-2021-43033

CVE-2021-43033 is a critical-severity vulnerability in Kaseya Unitrends Backup with a CVSS 3.x base score of 9.8. 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-78.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 10.0
EPSS exploit prediction: 6% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
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. 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.

Frequently asked questions

What is CVE-2021-43033?: 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.
How severe is CVE-2021-43033?: CVE-2021-43033 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43033 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43033?: CVE-2021-43033 affects Kaseya Unitrends Backup. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43033?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-43033 published?: CVE-2021-43033 was published on 2021-12-06 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Kaseya Unitrends Backup

CVE-2021-40386 — Critical (CVSS 9.8): Kaseya Unitrends Client/Agent through 10.5,5 allows remote attackers to execute arbitrary code.
CVE-2021-43044 — Critical (CVSS 9.8): An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The SNMP daemon was configured with a weak…
CVE-2021-43042 — Critical (CVSS 9.8): An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. A buffer overflow existed in the…
CVE-2021-43036 — Critical (CVSS 9.8): An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. The password for the PostgreSQL wguest…
CVE-2021-43035 — Critical (CVSS 9.8): An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. Two unauthenticated SQL injection…
CVE-2018-6328 — Critical (CVSS 9.8): It was discovered that the Unitrends Backup (UB) before 10.1.0 user interface was exposed to an authentication bypass,…

All CVEs affecting Kaseya Unitrends Backup →

Other CWE-78 (OS Command Injection) vulnerabilities

CVE-2026-56004 — Critical (CVSS 10.0): A shellcode injection in the mercurial handler of the obs tar_scm source service before version 0.12.4 could be used by…
CVE-2026-56415 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability within the debug.pl script that is…
CVE-2026-56413 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability in the ms_service.pl service, which listens…
CVE-2026-49869 — Critical (CVSS 10.0): Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, AuthenticationFilter in…
CVE-2026-49261 — Critical (CVSS 10.0): MariaDB server is a community developed fork of MySQL server. Versions 10.6.1 through 10.6.26, 10.11.1 through…
CVE-2026-10520 — Critical (CVSS 10.0): An OS Command Injection vulnerability in Ivanti Sentry before the R10.5.2, R10.6.2 and R10.7.1 versions allows a…

Browse all CWE-78 (OS Command Injection) vulnerabilities →