# CVE-2021-20729: Cross-site scripting in pfSense CE and pfSense Plus

> Remote attackers can inject arbitrary scripts via malicious URLs in pfSense, potentially compromising user sessions or executing code.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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:** 31 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-gmq9-rc2w-2c75

## What is CVE-2021-20729?

CVE-2021-20729 is a medium-severity cross-site scripting vulnerability in pfSense CE and pfSense Plus, published on 31 Mar 2022. 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

Cross-site scripting vulnerability in pfSense CE and pfSense Plus (pfSense CE software versions 2.5.2 and earlier, and pfSense Plus software versions 21.05 and earlier) allows a remote attacker to inject an arbitrary script via a malicious URL.

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

## Which versions are affected by CVE-2021-20729?

It affects 2 products.


Products: Netgate Pfsense Plus, Pfsense Pfsense.

## How do I fix CVE-2021-20729?

No fix has been published for CVE-2021-20729 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20729 being exploited?

There is no known exploitation of CVE-2021-20729 in the wild and no public exploit code.

## Other vulnerabilities in pfSense CE and pfSense Plus

- [CVE-2023-27100](https://insights.sbomify.com/CVE-2023-27100/): Security feature bypass in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20729 and fix it if it is affected.

What it is: CVE-2021-20729 is a medium-severity cross-site scripting vulnerability in pfSense CE and pfSense Plus, published on 31 Mar 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-20729 in the wild and no public exploit code.

Affected product: pfSense CE and pfSense Plus. 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-2021-20729/ (Markdown: https://insights.sbomify.com/CVE-2021-20729/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20729
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20729
- OSV: https://osv.dev/vulnerability/CVE-2021-20729

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20729/
Summaries are generated and may contain mistakes; the official description above is the record.