If Varnish receives a certain illegal request, and the subroutine 'vcl_error{}' restarts the request, the varnishd worker process will crash with an assert. The varnishd management process will restart the worker process, but there will be a brief interruption of service and the cache will be emptied, causing more traffic to go to the backend. Versions 2.0.x, 2.1.x, and 3.0.x are affected.
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