CVE-2021-44618 is a critical-severity (CVSS 9.8) Code Injection vulnerability in nystudio107/craft-seomatic. A fix is available for nystudio107/craft-seomatic — see the affected versions and patch details below.
Server-side Template Injection in nystudio107/craft-seomatic
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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
A Server-side Template Injection (SSTI) vulnerability exists in Nystudio107 Seomatic prior to 3.4.12 in src/helpers/UrlHelper.php via the host header.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | nystudio107/craft-seomatic | all versions | 3.4.12composer require nystudio107/craft-seomatic:^3.4.12 |
Affected Products
seomaticnystudio107Detection & 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 3.4.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-44618 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-2021-44618 in your dependencies?
Find it across Packagist, including transitive dependencies.