# CVE-2021-3811: Cross-site Scripting (XSS) - Reflected in pi-hole/adminlte

> Reflected Cross-Site Scripting in the Pi-hole admin interface allows attackers to execute arbitrary scripts in victim browsers.

- **Severity:** Medium 6.7 (`CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Sep 2021
- **Updated:** 3 Aug 2024

## What is CVE-2021-3811?

CVE-2021-3811 is a medium-severity cross-site scripting vulnerability in pi-hole/adminlte, published on 17 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

adminlte is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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

## Which versions are affected by CVE-2021-3811?

It affects 1 product.


Products: Pi-Hole Web Interface.

## How do I fix CVE-2021-3811?

No fix has been published for CVE-2021-3811 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-3811 being exploited?

There is no known exploitation of CVE-2021-3811 in the wild and no public exploit code.

## Other vulnerabilities in pi-hole/adminlte

- [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-2021-3811 and fix it if it is affected.

What it is: CVE-2021-3811 is a medium-severity cross-site scripting vulnerability in pi-hole/adminlte, published on 17 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3811 in the wild and no public exploit code.

Affected product: pi-hole/adminlte. 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-2021-3811/ (Markdown: https://insights.sbomify.com/CVE-2021-3811/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3811
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3811
- OSV: https://osv.dev/vulnerability/CVE-2021-3811

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3811/
Summaries are generated and may contain mistakes; the official description above is the record.