CVE-2020-27990
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 · uneditedNagios XI before 5.7.5 is vulnerable to XSS in the Deployment tool (add agent).
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 confidenceNagios XI before version 5.7.5 contains a stored cross-site scripting (XSS) vulnerability in the Deployment tool's 'add agent' functionality. User-supplied input in the agent configuration is not properly sanitized before being rendered in the web interface, allowing an authenticated attacker to inject malicious JavaScript code that executes in the context of other users' sessions.
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< 5.7.5CVSS 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
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
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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Confirm Nagios XI is installedAccess the web interface or check for Nagios XI directories and services on the server. Look for the typical Nagios XI URL path (such as /nagiosxi/) or check for the nagiosxi service/process.Affected if The system is running Nagios XI
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Identify the installed Nagios XI versionIn the web interface, navigate to the Admin > System Information page, or check the /usr/local/nagiosxi/etc/app.ini configuration file for the version number.Affected if The installed version is earlier than 5.7.5 (e.g., 5.7.4, 5.7.3, etc.)
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Verify the Deployment tool is accessibleLog into the Nagios XI web interface as an authenticated user and navigate to the Deployment section, typically found under the 'Deploy' or 'Deployment' menu option.Affected if The Deployment tool feature is present and accessible to authenticated users
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Check access to the Add Agent functionalityWithin the Deployment tool interface, locate the option to add a new agent (often labeled as 'Add Agent', 'New Agent', or similar). Confirm this functionality exists and is available for use.Affected if The 'add agent' functionality is available in the Deployment tool
The environment is affected if Nagios XI is installed with a version lower than 5.7.5 and the authenticated user can access the Deployment tool's 'add agent' functionality.
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.
From vendor data5.7.5
Upgrade to Nagios XI version 5.7.5 or later which includes proper input sanitization for the Deployment tool. If immediate patching is not possible, implement output encoding on the affected form fields as a compensating control.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-27990 — 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-2020-27990 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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