GHSA-h77w-655f-6j3m
HIGHGHSA-h77w-655f-6j3m is a high-severity (CVSS 8.8) Unrestricted File Upload vulnerability in silverstripe/cms. O3 Security confirms whether GHSA-h77w-655f-6j3m is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Silverstripe CMS malicious file upload enables script execution
Blast Radius
silverstripe/cmsReal-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 CMS through 4.5 can be susceptible to script execution from malicious upload contents under allowed file extensions (for example HTML code in a TXT file). When these files are stored as protected or draft files, the MIME detection can cause browsers to execute the file contents. Uploads stored as protected or draft files are allowed by default for authorised users only, but can also be enabled through custom logic as well as modules such as silverstripe/userforms. Sites using the previously optional silverstripe/mimevalidator module can configure MIME whitelists rather than extension whitelists, and hence prevent this issue. Sites on the Common Web Platform (CWP) use this module by default, and are not affected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | silverstripe/cms | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for silverstripe/cms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of silverstripe/cms has shipped for GHSA-h77w-655f-6j3m yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-h77w-655f-6j3m is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-h77w-655f-6j3m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-h77w-655f-6j3m in your dependencies?
O3 detects GHSA-h77w-655f-6j3m across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.