# CVE-2021-27902: Craft CMS Cross-site Scripting Vulnerability

> An XSS vulnerability in Craft CMS front-end forms allows attackers to inject malicious scripts via user uploads.

- **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:** Yes
- **Published:** 30 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-3jxh-789f-p7m6

## What is CVE-2021-27902?

CVE-2021-27902 is a medium-severity cross-site scripting vulnerability in Craftcms Craft Cms, published on 30 Jun 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

An issue was discovered in Craft CMS before 3.6.0. In some circumstances, a potential XSS vulnerability existed in connection with front-end forms that accepted user uploads.

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

## Which versions are affected by CVE-2021-27902?

2 open source packages ship an affected version, including craftcms/cms. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `craftcms/cms` | Packagist | All versions | 3.6.0 |
| `craftcms/cms` | Packagist | All versions | 3.6.0 |

Products: Craftcms Craft Cms.

## How do I fix CVE-2021-27902?

Upgrade craftcms/cms to 3.6.0 or later.

## Is CVE-2021-27902 being exploited?

There is no known exploitation of CVE-2021-27902 in the wild and no public exploit code.

## Other vulnerabilities in Craftcms Craft Cms

- [CVE-2025-32432](https://insights.sbomify.com/CVE-2025-32432/): Craft CMS Code Injection (critical 10.0, exploited in the wild)
- [CVE-2024-56145](https://insights.sbomify.com/CVE-2024-56145/): Craft CMS Code Injection (critical 9.3, exploited in the wild)
- [CVE-2025-23209](https://insights.sbomify.com/CVE-2025-23209/): Craft CMS Code Injection (high 8.1, exploited in the wild)
- [CVE-2025-35939](https://insights.sbomify.com/CVE-2025-35939/): Craft CMS External Control of Assumed-Immutable Web Parameter (medium 6.9, exploited in the wild)
- [CVE-2023-41892](https://insights.sbomify.com/CVE-2023-41892/): Craft CMS Remote Code Execution vulnerability (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27902 and fix it if it is affected.

What it is: CVE-2021-27902 is a medium-severity cross-site scripting vulnerability in Craftcms Craft Cms, published on 30 Jun 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: There is no known exploitation of CVE-2021-27902 in the wild and no public exploit code.

Affected packages and fixed versions:
- craftcms/cms (Packagist): affected all versions; fixed in 3.6.0
- craftcms/cms (Packagist): affected all versions; fixed in 3.6.0

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-2021-27902/ (Markdown: https://insights.sbomify.com/CVE-2021-27902/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27902
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27902
- OSV: https://osv.dev/vulnerability/CVE-2021-27902

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27902/
Summaries are generated and may contain mistakes; the official description above is the record.