# CVE-2021-43810: Cross-site Scripting (XSS) when redirect an url

> Attackers can execute malicious scripts via reflected XSS in the redirect URL parameter, affecting Admidio user management systems.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **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:** 7 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-3qgf-qgc3-42hh

## What is CVE-2021-43810?

CVE-2021-43810 is a high-severity cross-site scripting vulnerability in admidio, published on 7 Dec 2021. 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

Admidio is a free open source user management system for websites of organizations and groups. A cross-site scripting vulnerability is present in Admidio prior to version 4.0.12. The Reflected XSS vulnerability occurs because redirect.php does not properly validate the value of the url parameter. Through this vulnerability, an attacker is capable to execute malicious scripts. This issue is patched in version 4.0.12.

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

## Which versions are affected by CVE-2021-43810?

It affects 1 product.


Products: Admidio Admidio.

## How do I fix CVE-2021-43810?

No fix has been published for CVE-2021-43810 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-43810 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-43810 exists.

Public exploit code:

- Admidio - Cross-Site Scripting (nuclei): http/cves/2021/CVE-2021-43810.yaml

## Other vulnerabilities in admidio

- [CVE-2024-37906](https://insights.sbomify.com/CVE-2024-37906/): Admidio has Blind SQL Injection in ecard_send.php (critical 10.0)
- [CVE-2021-32630](https://insights.sbomify.com/CVE-2021-32630/): Various (critical 9.6)
- [CVE-2026-32817](https://insights.sbomify.com/CVE-2026-32817/): Admidio is Missing Authorization and CSRF Protection on Document and Folder Deletion (critical 9.1)
- [CVE-2024-38529](https://insights.sbomify.com/CVE-2024-38529/): Admidio Vulnerable to RCE via Arbitrary File Upload in Message Attachment (critical 9.1)
- [CVE-2026-32756](https://insights.sbomify.com/CVE-2026-32756/): Admidio: Unrestricted File Upload via CSRF Token Validation Bypass in Documents & Files Module (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43810 and fix it if it is affected.

What it is: CVE-2021-43810 is a high-severity cross-site scripting vulnerability in admidio, published on 7 Dec 2021. 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-2021-43810 exists.

Affected product: admidio. 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-2021-43810/ (Markdown: https://insights.sbomify.com/CVE-2021-43810/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43810
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43810
- OSV: https://osv.dev/vulnerability/CVE-2021-43810

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43810/
Summaries are generated and may contain mistakes; the official description above is the record.