CVE-2020-9757 is a critical-severity (CVSS 9.8) CWE-74 vulnerability in nystudio107/craft-seomatic. 1 public exploit reference exists, so weaponization risk is real. A fix is available for nystudio107/craft-seomatic — see the affected versions and patch details below.
SEOmatic for CraftCMS allows Server-Side Template Injection
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-9757 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 376,715 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
nystudio107/craft-seomaticReal-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
The SEOmatic component before 3.3.0 for Craft CMS allows Server-Side Template Injection that leads to RCE via malformed data to the metacontainers controller.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | nystudio107/craft-seomatic | all versions | 3.3.0composer require nystudio107/craft-seomatic:^3.3.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nystudio107/craft-seomatic, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nystudio107/craft-seomatic to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-9757 is resolved across your whole dependency graph.
Workarounds
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2020-9757 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-9757. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2020-9757
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2020-9757 -u https://target- Template
- Craft CMS < 3.3.0 - Server-Side Template Injection
- Severity
- critical
- Impact
- Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the server.
- Remediation
- Upgrade Craft CMS to version 3.3.0 or higher to mitigate this vulnerability.
Template by ProjectDiscovery nuclei-templates (dwisiswant0), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2020-9757 in your dependencies?
O3 Security finds CVE-2020-9757 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.