GHSA-m884-279h-32v2 is a medium-severity (CVSS 4.6) vulnerability in symfony/error-handler. O3 Security confirms whether GHSA-m884-279h-32v2 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Exceptions displayed in non-debug configurations in Symfony
Real-World Exposure
symfony/error-handler🐘symfony/error-handler🐘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
Description
When ErrorHandler renders an exception HTML page, it uses un-escaped properties from the related Exception class to render the stacktrace. The security issue comes from the fact that the stacktraces were also displayed in non-debug environments.
Resolution
The ErrorHandler class now escapes all properties coming from the related Exception, and the stacktrace is not displayed anymore in non-debug environments.
The patches for this issue are available here and here for branch 4.4.
Credits
I would like to thank Luka Sikic for reporting & Yonel Ceruto and Jérémy Derussé for fixing the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/error-handler | ≥ 4.4.0&&< 4.4.4 | 4.4.4 |
| 🐘Packagist | symfony/error-handler | ≥ 5.0.0&&< 5.0.4 | 5.0.4 |
| 🐘Packagist | symfony/symfony | ≥ 4.4.0&&< 4.4.4 | 4.4.4 |
| 🐘Packagist | symfony/symfony | ≥ 5.0.0&&< 5.0.4 | 5.0.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/error-handler. 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/error-handler to 4.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m884-279h-32v2 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 GHSA-m884-279h-32v2 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-m884-279h-32v2. 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-m884-279h-32v2 in your dependencies?
O3 detects GHSA-m884-279h-32v2 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.