CVE-2020-5274: 
PHP vulnerability analysis and mitigation

CVE-2020-5274 is a security vulnerability in Symfony's ErrorHandler component that was disclosed on March 30, 2020. The vulnerability affects Symfony versions >=4.4.0, <4.4.4 and >=5.0.0, <5.0.4. When ErrorHandler renders an exception HTML page, it uses un-escaped properties from the related Exception class to render the stacktrace, potentially exposing sensitive information in non-debug environments (GitHub Advisory).

The vulnerability stems from the ErrorHandler component not properly escaping exception properties when rendering stacktraces in HTML error pages. This issue was particularly concerning because stacktraces were being displayed even in non-debug environments, potentially exposing sensitive application information. The vulnerability was assigned a CVSS v3 score indicating moderate severity (GitHub Advisory).

The vulnerability could allow attackers to view sensitive information through unescaped exception properties in stacktraces, even in production environments where such debug information should not be visible. This could potentially expose internal application details and system information that could be used for further attacks (GitHub Advisory).

The vulnerability requires no special privileges to exploit, as it affects the error handling functionality that is accessible to any user who can trigger an exception in the application. The issue was discovered and reported by Luka Sikic (GitHub Advisory).

The issue was patched in Symfony versions 4.4.4 and 5.0.4. The fix includes proper escaping of all properties coming from Exception classes and ensures that stacktraces are not displayed in non-debug environments. Users should upgrade to these patched versions or later to resolve the vulnerability (GitHub Advisory).