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Fencer Vulns
critical 9.8

CVE-2021-43033 json

An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5.

published 2021-12-06 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-29987

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
6.2%
EPSS 6.2% chance of exploitation in 30 days, percentile 93%
public exploits
0
none known

Summary

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.

Patch / fix

  • kaseya unitrends_backup 10.5.5

Exploit prediction

6.19% chance of exploitation in the next 30 days, higher than 93% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • cyberonesecurity.com https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-1 referenced PoC, tagged "exploit" by a source, unverified
  • cyberonesecurity.com https://www.cyberonesecurity.com/blog/exploiting-kaseya-unitrends-backup-appliance-part-2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 10.0 AV:N/AC:L/Au:N/C:C/I:C/A:C

Classification

Weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS Command

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.