# CVE-2026-54721: Silverstripe UserForms: Remote code execution via userforms email subject

> Authenticated CMS users can execute arbitrary server-side code via the email subject field in Silverstripe UserForms.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** GHSA-g8wr-r2v2-vqc6

## What is CVE-2026-54721?

CVE-2026-54721 is a high-severity code injection vulnerability in silverstripe-userforms, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Silverstripe UserForms provides a visual form builder for the Silverstripe CMS. From 6.0.0 until 6.4.9, 7.0.7, and 7.1.1, the userform email recipient subject field in the CMS accepts a specially crafted payload that can be interpreted as executable server-side code. An authenticated CMS user with permission to configure a UserForms email recipient can use the subject field to run arbitrary code on the server, compromising confidentiality, integrity, and availability. This issue is fixed in versions 6.4.9, 7.0.7, and 7.1.1.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-54721?

6 open source packages ship an affected version, including silverstripe/userforms.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `silverstripe/userforms` | Packagist | All versions | 6.4.9 |
| `silverstripe/userforms` | Packagist | All versions | 6.4.9 |
| `silverstripe/userforms` | Packagist | From 7.0.0 | 7.0.7 |
| `silverstripe/userforms` | Packagist | From 7.0.0 | 7.0.7 |
| `silverstripe/userforms` | Packagist | From 7.1.0 | 7.1.1 |
| `silverstripe/userforms` | Packagist | From 7.1.0 | 7.1.1 |

## How do I fix CVE-2026-54721?

Upgrade silverstripe/userforms to a fixed version for your release line: 6.4.9, 7.0.7 or 7.1.1.

## Is CVE-2026-54721 being exploited?

There is no known exploitation of CVE-2026-54721 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54721 and fix it if it is affected.

What it is: CVE-2026-54721 is a high-severity code injection vulnerability in silverstripe-userforms, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-54721 in the wild and no public exploit code.

Affected packages and fixed versions:
- silverstripe/userforms (Packagist): affected all versions; fixed in 6.4.9
- silverstripe/userforms (Packagist): affected all versions; fixed in 6.4.9
- silverstripe/userforms (Packagist): affected from 7.0.0; fixed in 7.0.7
- silverstripe/userforms (Packagist): affected from 7.0.0; fixed in 7.0.7
- silverstripe/userforms (Packagist): affected from 7.1.0; fixed in 7.1.1
- silverstripe/userforms (Packagist): affected from 7.1.0; fixed in 7.1.1

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-2026-54721/ (Markdown: https://insights.sbomify.com/CVE-2026-54721/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54721
- OSV: https://osv.dev/vulnerability/CVE-2026-54721

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54721/
Summaries are generated and may contain mistakes; the official description above is the record.