CVE-2019-10909 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in symfony/symfony. A fix is available for symfony/symfony — see the affected versions and patch details below.
Symfony Cross-site Scripting (XSS) vulnerability
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2019-10909 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/framework-bundle🐘symfony/framework-bundle🐘symfony/framework-bundle+6 moreReal-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
In Symfony before 2.7.51, 2.8.x before 2.8.50, 3.x before 3.4.26, 4.x before 4.1.12, and 4.2.x before 4.2.7, validation messages are not escaped, which can lead to XSS when user input is included. This is related to symfony/framework-bundle.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/symfony | ≥ 2.7.0&&< 2.7.51 | 2.7.51composer require symfony/symfony:^2.7.51 |
| 🐘Packagist | symfony/symfony | ≥ 2.8.0&&< 2.8.50 | 2.8.50composer require symfony/symfony:^2.8.50 |
| 🐘Packagist | symfony/symfony | ≥ 3.0.0&&< 3.4.26 | 3.4.26composer require symfony/symfony:^3.4.26 |
| 🐘Packagist | symfony/symfony | ≥ 4.0.0&&< 4.1.12 | 4.1.12composer require symfony/symfony:^4.1.12 |
| 🐘Packagist | symfony/symfony | ≥ 4.2.0&&< 4.2.7 | 4.2.7composer require symfony/symfony:^4.2.7 |
| 🐘Packagist | symfony/framework-bundle | ≥ 2.7.0&&< 2.7.51 | 2.7.51composer require symfony/framework-bundle:^2.7.51 |
Affected Products
drupaldrupalsymfonysensiolabsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/symfony, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update symfony/symfony to 2.7.51 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-10909 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2019-10909 in your dependencies?
Find it across Packagist, including transitive dependencies.