dbcve.org
Unitrends BackupApplication · Kaseya

CVE-2021-43042

CRITICAL · 9.8 CVSS v3.1 Published 2021-12-06
Fix available
A fix is available. Upgrade to 10.5.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue was discovered in Kaseya Unitrends Backup Appliance before 10.5.5. A buffer overflow existed in the vaultServer component. This was exploitable by a remote unauthenticated attacker.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-120

A fixed-size buffer is filled without checking the length of the incoming data, so it overflows into neighbouring memory. This is the classic overflow attackers use to overwrite return addresses and hijack execution. The fix is strict length checks and safe, bounded string and memory functions.

General guidance for the classic buffer overflow class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Unitrends BackupApplication
Affected:>= 10.0, < 10.5.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.5.5 or later
Fixed in 10.5.5
Recommended fix Moderate confidence

Unitrends Backup 10.5.5 or later

  1. 1. Backup all critical data and verify backup integrity before proceeding with the upgrade.
  2. 2. Schedule a maintenance window as the upgrade may require downtime.
  3. 3. Download the Unitrends Backup 10.5.5 (or latest available) upgrade package from the official Kaseya/Unitrends portal.
  4. 4. Follow the standard Unitrends Backup upgrade procedure: stop all backup jobs and services, then initiate the upgrade via the web console or CLI.
  5. 5. After upgrade completes, verify the vaultServer component is running correctly.
  6. 6. Confirm the version by checking System > About in the Unitrends Backup interface to ensure version 10.5.5 or later is installed.
  7. 7. Test critical backup and restore operations to verify system functionality.
Caveat Review Kaseya Unitrends release notes for version 10.5.5 for any configuration or feature changes that may require adjustment

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $3,550. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-43042 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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