CVE-2019-18886
MEDIUMCVE-2019-18886 is a medium-severity (CVSS 5.3) CWE-203 vulnerability in symfony/security-http. O3 Security confirms whether CVE-2019-18886 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
User enumeration leak using switch user functionality in Symfony
Real-World Exposure
symfony/security-http🐘symfony/security-http🐘symfony/symfony🐘symfony/symfonyReal-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
An issue was discovered in Symfony 4.2.0 to 4.2.11 and 4.3.0 to 4.3.7. The ability to enumerate users was possible due to different handling depending on whether the user existed when making unauthorized attempts to use the switch users functionality. This is related to symfony/security.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/security-http | ≥ 4.1.0&&< 4.2.12 | 4.2.12 |
| 🐘Packagist | symfony/security-http | ≥ 4.3.0&&< 4.3.8 | 4.3.8 |
| 🐘Packagist | symfony/symfony | ≥ 4.1.0&&< 4.2.12 | 4.2.12 |
| 🐘Packagist | symfony/symfony | ≥ 4.3.0&&< 4.3.8 | 4.3.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/security-http. 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.
Fix
Update symfony/security-http to 4.2.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-18886 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 pinpoints whether CVE-2019-18886 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 CVE-2019-18886. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2019-18886 in your dependencies?
O3 detects CVE-2019-18886 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.