The affected asset is vulnerable to this vulnerability ONLY if it is running one of the following modules: mod_http2. Review your web server configuration for validation. By manipulating the flow control windows on streams, a client was able to block server threads for long times, causing starvation of worker threads. Connections could still be opened, but no streams where processed for these. This issue affected HTTP/2 support in 2.4.17 and 2.4.18.