CVE-2021-32778

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy’s procedure for resetting a HTTP/2 stream has O(N^2) complexity, leading to high CPU utilization when a large number of streams are reset. Deployments are susceptible to Denial of Service when Envoy is configured with high limit on H/2 concurrent streams. An attacker wishing to exploit this vulnerability would require a client opening and closing a large number of H/2 streams. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to reduce time complexity of resetting HTTP/2 streams. As a workaround users may limit the number of simultaneous HTTP/2 dreams for upstream and downstream peers to a low number, i.e. 100.

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy’s procedure for resetting a HTTP/2 stream has O(N^2) complexity, leading to high CPU utilization when a large number of streams are reset. Deployments are susceptible to Denial of Service when Envoy is configured with high limit on H/2 concurrent streams. An attacker wishing to exploit this vulnerability would require a client opening and closing a large number of H/2 streams. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to reduce time complexity of resetting HTTP/2 streams. As a workaround users may limit the number of simultaneous HTTP/2 dreams for upstream and downstream peers to a low number, i.e. 100.

Envoy es un proxy L7 de código abierto y un bus de comunicación diseñado para grandes arquitecturas modernas orientadas a servicios. En las versiones afectadas, el procedimiento de Envoy para restablecer un flujo HTTP/2 presenta una complejidad O(N^2), conllevando a un alto uso de la CPU cuando se restablece un gran número de flujos. Los despliegues son susceptibles a una Denegación de Servicio cuando Envoy está configurado con un alto límite de flujos concurrentes H/2. Un atacante que desee explotar esta vulnerabilidad necesitaría un cliente que abriera y cerrara un gran número de flujos H/2. Envoy versiones 1.19.1, 1.18.4, 1.17.4 y 1.16.5, contienen correcciones para reducir la complejidad del tiempo de restablecimiento de los flujos HTTP/2. Como solución, los usuarios pueden limitar el número de sueños HTTP/2 simultáneos para los pares ascendentes y descendentes a un número bajo, es decir, 100.