CVE-2021-41238: 
C# vulnerability analysis and mitigation

Hangfire, an open-source system for background job processing in .NET and .NET Core applications, was affected by a security vulnerability in version 1.7.25. The vulnerability (CVE-2021-41238) involved a regression in the Dashboard UI's default authorization settings, where no authorization filters were being used by default, allowing unauthorized remote access to sensitive data (GitHub Advisory).

The vulnerability stems from a change in version 1.7.25 where the default LocalRequestsOnlyAuthorizationFilter was not being applied to the Dashboard UI. This filter was designed to allow only local requests and prohibit remote requests as a security measure. Without this filter, remote requests could succeed without proper authorization. The issue specifically affects installations using the UseHangfireDashboard method with default DashboardOptions.Authorization property value (GitHub Advisory).

The vulnerability allows unauthorized remote access to the Hangfire Dashboard UI, potentially exposing sensitive data and system information to unauthorized users. This affects installations where no custom authorization rules are configured, which is a common default setup as recommended in the documentation (GitHub Advisory).

The issue was patched in version 1.7.26, which restored the default authorization rules to prohibit remote requests by including the LocalRequestsOnlyAuthorizationFilter. For users unable to upgrade, a workaround is available by explicitly configuring the LocalRequestsOnlyAuthorizationFilter in the Dashboard UI setup. This can be done by adding the filter to the DashboardOptions.Authorization property (GitHub Advisory).