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.

References

• GHSA-m884-279h-32v2
• symfony/symfony@629d21b
• symfony/symfony@cf80224
• https://nvd.nist.gov/vuln/detail/CVE-2020-5274
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/error-handler/CVE-2020-5274.yaml
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2020-5274.yaml
• https://symfony.com/cve-2020-5274