dbcve.org
FusionApplication · Nagios

CVE-2017-20209

MEDIUM · 6.1 CVSS v3.1 Published 2025-10-30
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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
Nagios Fusion versions prior to 4.0.1 are vulnerable to cross-site scripting (XSS) via the Users and Servers pages. 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 confidence

Nagios Fusion versions prior to 4.0.1 contain a stored cross-site scripting (XSS) vulnerability in the Users and Servers pages. The application fails to properly validate or escape user-supplied input, allowing authenticated attackers to inject malicious JavaScript that executes in the context of other users' browsers when they view the affected pages.

MitigationUpgrade Nagios Fusion to version 4.0.1 or later which addresses the insufficient input validation. Until upgraded, consider disabling user account creation/modification and restricting access to the Servers page.

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
FusionApplication
Affected:= 4.0.0

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Nagios Fusion version
    Locate the Nagios Fusion installation directory and check the version file, or access the web interface and look for the version number typically displayed in the footer or about page
    Affected if The installed version is exactly 4.0.0 (prior to the 4.0.1 patch)
  2. Confirm web interface is accessible
    Access the Nagios Fusion web interface URL in a browser or verify the web service is running and reachable on the configured port (typically 80 or 443)
    Affected if The web interface is accessible over the network, allowing potential attackers to reach the login page
  3. Verify authentication is enabled
    Check if the web interface requires login credentials and that user accounts exist in the system
    Affected if The application allows user authentication, which is required for an authenticated attacker to inject the malicious JavaScript
  4. Identify access to Users or Servers pages
    Log into the web interface and navigate to the Users page and Servers page to confirm these features are available and accessible
    Affected if The authenticated user has access to either the Users page or Servers page where the XSS vulnerability exists

A user is affected if Nagios Fusion version 4.0.0 is installed, the web interface is accessible, and authenticated users can access the Users or Servers pages where unsanitized input can be stored and executed in other users' browsers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Nagios Fusion to version 4.0.1 or later which addresses the insufficient input validation. Until upgraded, consider disabling user account creation/modification and restricting access to the Servers page.

Recommended fix Moderate confidence

Nagios Fusion 4.0.1

  1. Download Nagios Fusion version 4.0.1 or later from the official Nagios website
  2. Backup your current Nagios Fusion installation and configuration database
  3. Stop the Nagios Fusion services before upgrading
  4. Install the version 4.0.1 package using the appropriate package manager or installer for your operating system
  5. Restart the Nagios Fusion services after installation
  6. Verify the upgrade was successful by accessing the Nagios Fusion web interface
  7. Test the Users and Servers pages to confirm the XSS vulnerability is mitigated

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

Fix this in Fusion Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2017-20209 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data