CVE-2018-20753
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 · uneditedKaseya VSA RMM before R9.3 9.3.0.35, R9.4 before 9.4.0.36, and R9.5 before 9.5.0.5 allows unprivileged remote attackers to execute PowerShell payloads on all managed devices. In January 2018, attackers actively exploited this vulnerability in the wild.
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 · high confidenceKaseya VSA RMM contains an authentication bypass vulnerability allowing unprivileged remote attackers to execute arbitrary PowerShell payloads on all devices managed by the VSA platform. This supply-chain vulnerability enables mass compromise of managed endpoints through the RMM infrastructure.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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>= 9.3, < 9.3.0.35>= 9.4, < 9.4.0.36>= 9.5, < 9.5.0.5CVSS 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
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Kaseya VSA installation and versionOpen Windows Control Panel > Programs and Features, or check Add/Remove Programs. Look for 'Kaseya VSA' or 'Kaseya Virtual System Administrator' and note the version number shown.Affected if The installed version matches one of these ranges: 9.3.x where x < 35, 9.4.x where x < 36, or 9.5.x where x < 5 (for example, 9.3.0.10 or 9.5.0.1 would be affected).
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Check VSA web interface versionAccess the Kaseya VSA web portal (typically https://your-server:443 or https://your-server:4430). The login page or About section usually displays the version. If you cannot log in, the version may still be visible in the HTTP response headers or the page source.Affected if The reported version falls within the affected ranges listed above.
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Check VSA service version via PowerShellOpen PowerShell and run 'Get-Service | Where-Object {$_.Name -like "*Kaseya*"} | Select-Object Name, DisplayName, Status'. Then check the executable path with '(Get-Service -Name "ServiceName").BinaryPathName' to locate the installation directory. Check the file version of the main VSA executable.Affected if The executable file version is below 9.3.0.35, 9.4.0.36, or 9.5.0.5 respectively.
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Assess network exposureDetermine if the VSA web interface is accessible from the internet or untrusted networks. Check firewall rules, NAT configurations, or reverse proxy settings that expose ports 443, 4430, or 80 to external IPs. Use 'netstat -an | findstr :443' or your firewall logs to identify listening interfaces.Affected if The VSA server is directly exposed to the internet or untrusted networks without VPN or IP allow-listing, and the version is within the affected ranges.
You are affected if your Kaseya VSA installation version is 9.3.0.34 or lower, 9.4.0.35 or lower, or 9.5.0.4 or lower, and the management interface is reachable from the network where attackers could send malicious requests.
Generated from the published advisory. Verify against your own configuration.
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 · scoped9.3.0.359.4.0.369.5.0.5
Apply vendor patches (R9.3 ≥9.3.0.35, R9.4 ≥9.4.0.36, R9.5 ≥9.5.0.5). Given active in-the-wild exploitation, prioritize immediate deployment. Monitor for suspicious PowerShell execution and review VSA access logs.
Upgrade to 9.3.0.35 (for 9.3 branch), 9.4.0.36 (for 9.4 branch), or 9.5.0.5 (for 9.5 branch)
- Identify the current Kaseya VSA version by checking the About or System Information page in the VSA admin interface
- Determine which version branch you are on (9.3, 9.4, or 9.5)
- Create a complete backup of the Kaseya VSA database and configuration settings
- Download the appropriate patched version from the Kaseya Knowledge Base or partner portal: version 9.3.0.35 for the 9.3 branch, 9.4.0.36 for the 9.4 branch, or 9.5.0.5 for the 9.5 branch
- Stop all Kaseya VSA services before applying the upgrade
- Apply the upgrade following the official Kaseya upgrade documentation
- Restart Kaseya VSA services and verify the system is operational
- Confirm the installed version matches the expected patched version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing16.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-20753 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-20753 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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