{"id":"CVE-2021-32778","state":"PUBLISHED","title":"Excessive CPU utilization when closing HTTP/2 streams","description":"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.","publishedAt":"2021-08-24T20:30:11.000Z","updatedAt":"2024-08-03T23:33:55.854Z","severity":{"score":5.8,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["envoyproxy envoy"],"affected":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":">= 1.19.0, < 1.19.1","status":"affected"},{"version":">= 1.18.0, < 1.18.4","status":"affected"},{"version":">= 1.17.0, < 1.17.4","status":"affected"},{"version":">= 1.16.0, < 1.16.5","status":"affected"}]}],"references":["https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history","https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chcc"],"weaknesses":["CWE-834"],"ingestedAt":"2026-10-29T19:48:33.225Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/32xxx/CVE-2021-32778.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-32778","state":"PUBLISHED","datePublished":"2021-08-24T20:30:11.000Z","dateUpdated":"2024-08-03T23:33:55.854Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2021-05-12T00:00:00.000Z"},"containers":{"cna":{"title":"Excessive CPU utilization when closing HTTP/2 streams","descriptions":[{"lang":"en","value":"Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. 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