Varnish Cache is a high-performance HTTP accelerator. It stores web pages in memory so web servers don"t have to create the same web page over and over again, giving the website a significant speed up. Security Fix: * varnish: HTTP/2 Broken Window Attack may result in denial of service For more details about the security issue, including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page listed in the References section.