CVE-2026-54721 is a high-severity (CVSS 8.8) Code Injection vulnerability in silverstripe/userforms. A fix is available for silverstripe/userforms — see the affected versions and patch details below.
Silverstripe UserForms: Remote code execution via userforms email subject
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54721.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-54721 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
silverstripe/userforms🐘silverstripe/userforms🐘silverstripe/userformsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | silverstripe/userforms | all versions | 6.4.9composer require silverstripe/userforms:^6.4.9 |
| 🐘Packagist | silverstripe/userforms | ≥ 7.0.0&&< 7.0.7 | 7.0.7composer require silverstripe/userforms:^7.0.7 |
| 🐘Packagist | silverstripe/userforms | ≥ 7.1.0&&< 7.1.1 | 7.1.1composer require silverstripe/userforms:^7.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for silverstripe/userforms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update silverstripe/userforms to 6.4.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54721 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2026-54721 in your dependencies?
Find it across Packagist, including transitive dependencies.