CVE-2026-33403
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 · uneditedPi-hole Admin Interface is a web interface for managing Pi-hole, a network-level ad and internet tracker blocking application. From 6.0 to before 6.5, a reflected DOM-based XSS vulnerability in taillog.js allows an unauthenticated attacker to inject arbitrary HTML into the Pi-hole admin interface by crafting a malicious URL. The file query parameter is interpolated into an innerHTML assignment without escaping. Because the Content-Security-Policy is missing the form-action directive, injected <form> elements can exfiltrate credentials to an external origin. This vulnerability is fixed in 6.5.
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 confidenceA reflected DOM-based XSS vulnerability in taillog.js allows unauthenticated attackers to inject arbitrary HTML via the file query parameter, which is unsafely interpolated into innerHTML without escaping. The missing form-action directive in the Content-Security-Policy allows injected form elements to exfiltrate credentials to external origins.
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>= 6.0, <= 6.4.1CVSS 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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Check Pi-hole Admin Interface versionAccess the web interface footer or use command: pihole -v (or check /etc/pihole/setupVars.conf), or query the API at /api/authAffected if version is 6.0 through 6.4.1 inclusive
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Locate taillog.js in the web rootOn the Pi-hole server, find the taillog.js file in the admin web directory (typically /var/www/html/admin/scripts/pi-hole/js/taillog.js or similar path)Affected if the file exists and contains innerHTML assignments using a file parameter without escaping
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Inspect taillog.js for unsafe innerHTML usageOpen taillog.js and search for patterns like 'innerHTML' combined with the 'file' query parameter or URL parametersAffected if code uses innerHTML to insert the file parameter value without sanitization/escaping
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Check Content-Security-Policy headersUse browser devtools or curl to inspect response headers from any Pi-hole page: curl -I http://<pihole-ip>/admin/Affected if the CSP header is missing the 'form-action' directive
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Test for reflected parameter in taillog functionalityAccess the taillog feature via browser at /admin/taillog.php?file=test, view page source, and check if the file parameter value appears unsafely in the HTMLAffected if the file parameter value is reflected directly in the DOM without encoding
You are affected if Pi-hole Admin Interface version is between 6.0 and 6.4.1 and the taillog feature reflects the file parameter unsafely into innerHTML with a CSP lacking form-action.
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 · scopedUpgrade Pi-hole Admin Interface to version 6.5 or later, which includes proper escaping of the file parameter and adds the form-action directive to the CSP.
6.5
- Backup your current Pi-hole configuration before upgrading
- Upgrade Pi-hole Admin Interface to version 6.5
- After upgrade, verify the taillog.js file now properly escapes the file query parameter before innerHTML assignment
- Confirm the Content-Security-Policy now includes the form-action directive
- Test that the admin interface functions normally after the upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation0.5 h
- Testing1.0 h
- Review / QA0.5 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33403 — 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-2026-33403 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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