CVE-2021-47699
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 versions prior to 5.8.7 are vulnerable to cross-site scripting (XSS) via the Audit Log page’s Send to NLS form. Insufficient validation or escaping of user-supplied input may allow an attacker to inject and execute arbitrary script in the context of a victim's browser.
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 versions before 5.8.7 contain a reflected XSS vulnerability in the Audit Log page's Send to NLS (Nagios Log Server) form. The application fails to properly validate or escape user-supplied input before rendering it in the browser, allowing an attacker to inject malicious JavaScript that executes in the context of a victim's session.
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< 5.8.7CVSS 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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Check Nagios XI versionLog into the Nagios XI web interface as an administrator. Navigate to the 'Admin' > 'System Information' page, or run the command 'cat /usr/local/nagiosxi/var/xi-sys.cfg' to retrieve the installed version number.Affected if The installed version is below 5.8.7 (for example, 5.8.6, 5.8.5, 5.7.x, etc.)
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Access Audit Log pageIn the Nagios XI web interface, navigate to 'Audit Logs' under the 'Reports' or 'Admin' section, depending on your navigation structure.Affected if The Audit Log page loads successfully and is accessible to your user account.
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Locate Send to NLS formOn the Audit Log page, look for the 'Send to NLS' or 'Send to Nagios Log Server' form or button, typically found in the filtering or export options of the audit log viewer.Affected if The Send to NLS form is present and available for use on the Audit Log page.
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Check if user input is reflected without encodingIn the Send to NLS form, enter a test string containing special characters (such as <script>alert('XSS')</script> or a similar benign payload) into available input fields (such as server URL, destination name, or filter parameters), then submit the form and inspect the page response or error messages to see if the input is rendered literally without HTML encoding.Affected if The submitted test string appears in the page response without being HTML-encoded (e.g., visible as <script> tags rather than being rendered as harmless text or escaped characters).
A user is affected if their Nagios XI version is below 5.8.7 AND they have access to the Audit Log page with the Send to NLS form, AND unsanitized user input is reflected in the response.
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 · scoped5.8.7
Upgrade to Nagios XI version 5.8.7 or later. As an interim measure, restrict access to the Audit Log page to trusted users only and implement Web Application Firewall rules to detect and block XSS payloads.
Nagios XI 5.8.7
- Back up the current Nagios XI installation and database before proceeding with the upgrade
- Download Nagios XI version 5.8.7 or later from the official Nagios website (www.nagios.com)
- Run the Nagios XI update script or use the web-based update mechanism to apply the upgrade
- After upgrade completes, clear browser cache and verify the Audit Log page's Send to NLS form now properly sanitizes input
- Confirm the version number reflects the update (should show 5.8.7 or later in the About page)
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-47699 — 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-2021-47699 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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- Version or environment caveats, and links to real fixes
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