# CVE-2026-33406: Pi-hole has a Stored HTML attribute injection

> Attackers can inject HTML attributes via malicious backups to alter UI styling, bypassing CSP restrictions in the Pi-hole admin interface.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-9rfm-c5g6-538p

## What is CVE-2026-33406?

CVE-2026-33406 is a medium-severity cross-site scripting vulnerability in pi-hole web, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Pi-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, configuration values from the /api/config endpoint are placed directly into HTML value="" attributes without escaping in settings-advanced.js, enabling HTML attribute injection. A double quote in any config value breaks out of the attribute context. JavaScript execution is blocked by the server's CSP (script-src 'self'), but injected attributes can alter element styling for UI redressing. The primary attack vector is importing a malicious teleporter backup, which bypasses per-field server-side validation. This vulnerability is fixed in 6.5.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-33406?

It affects 1 product.


Products: Pi-Hole Web Interface.

## How do I fix CVE-2026-33406?

No fix has been published for CVE-2026-33406 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-33406 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33406 exists.

## Other vulnerabilities in pi-hole web

- [CVE-2026-33765](https://insights.sbomify.com/CVE-2026-33765/): Pi-hole Web Interface has a Command Injection Vulnerability (high 8.9)
- [CVE-2023-23614](https://insights.sbomify.com/CVE-2023-23614/): Improper session handling of "Remember me for 7 days" functionality (high 8.8)
- [CVE-2025-59151](https://insights.sbomify.com/CVE-2025-59151/): Pi-hole Admin Interface vulnerable to HTTP response header injection via CRLF injection (high 8.2)
- [CVE-2021-3706](https://insights.sbomify.com/CVE-2021-3706/): Sensitive Cookie Without 'HttpOnly' Flag in pi-hole/adminlte (high 7.4)
- [CVE-2021-41175](https://insights.sbomify.com/CVE-2021-41175/): Stored XSS in Client Groups Management (Authenticated) (high 7.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33406 and fix it if it is affected.

What it is: CVE-2026-33406 is a medium-severity cross-site scripting vulnerability in pi-hole web, published on 6 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33406 exists.

Affected product: pi-hole web. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33406/ (Markdown: https://insights.sbomify.com/CVE-2026-33406/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33406
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33406
- OSV: https://osv.dev/vulnerability/CVE-2026-33406

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33406/
Summaries are generated and may contain mistakes; the official description above is the record.