CVE-2021-33179
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 · uneditedThe general user interface in Nagios XI versions prior to 5.8.4 is vulnerable to authenticated reflected cross-site scripting. An authenticated victim, who accesses a specially crafted malicious URL, would unknowingly execute the attached payload.
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 prior to 5.8.4 contain an authenticated reflected cross-site scripting (XSS) vulnerability in the general user interface. Attackers craft malicious URLs containing JavaScript payloads that execute within an authenticated victim's browser session when visited.
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< 5.8.4CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Confirm Nagios XI is installedCheck if the Nagios XI web interface is accessible or look for Nagios XI installation directories on the server (commonly /usr/local/nagiosxi or /opt/nagiosxi)Affected if Nagios XI is present on the system
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Identify the installed Nagios XI versionAccess the Nagios XI web interface and navigate to the About or System Information page (typically Admin > System Information > Version Info), or run the command 'cat /usr/local/nagiosxi/etc/backend/version' if the installation directory is knownAffected if The displayed version number is lower than 5.8.4
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Verify the vulnerability is presentThis is a reflected XSS in the general UI - the vulnerability requires an authenticated user to visit a crafted malicious URL. Check if the installed version is below 5.8.4 as the XSS exists in those versions.Affected if The installed version is below 5.8.4 and the system accepts authenticated user sessions
A user is affected if Nagios XI is installed with a version lower than 5.8.4 and allows authenticated user access to the web interface.
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 · scoped5.8.4
Upgrade Nagios XI to version 5.8.4 or later to remediate this vulnerability.
Nagios XI 5.8.4
- Backup the current Nagios XI installation and database before proceeding with the upgrade
- Log into the Nagios XI web interface as an administrative user
- Navigate to the Admin > System Information > System Settings menu
- Click the 'Check for Updates' button or use the built-in update mechanism
- Upgrade to Nagios XI version 5.8.4 or later
- After the upgrade completes, verify the version number matches the target release
- Clear browser cache and test that the application functions normally
- Confirm the XSS vulnerability is no longer present by attempting to access a previously malicious URL
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-33179 — 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-2021-33179 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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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.
- 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