{"schemaVersion":3,"id":"CVE-2021-32778","aliases":["RHEA-2021:4051"],"status":"published","duplicateOf":null,"title":null,"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.","dates":{"published":"2021-08-24T20:30:11.000Z","modified":"2024-08-03T23:33:55.854Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":7.5,"severity":"high","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":5.8,"severity":"medium","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Red hat","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":10,"impact":6,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":7.5,"severity":"high","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","exploitability":null,"impact":null,"computed":false},{"version":"2.0","versionLabel":"v2.0","source":"NVD","score":5,"severity":"medium","vector":"AV:N/AC:L/Au:N/C:N/I:N/A:P","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.0123,"percentile":0.68492,"severity":"low","asOf":"2026-10-19T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-19T00:00:00.000Z","baselineScore":0.0123},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.0123,"percentile":0.68492}],"last30":[{"date":"2026-09-19T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.0123,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.0123,"percentile":0.68492}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-834","name":"Excessive Iteration","description":"The product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed.","type":"weakness","status":"Incomplete","abstraction":"Class","likelihoodOfExploit":null,"url":"https://cwe.mitre.org/data/definitions/834.html"}],"affected":[{"vendor":"envoyproxy","product":"envoy","name":"envoy","label":"envoy","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 1.19.0, < 1.19.1","noFixRecorded":false,"fixedIn":null},{"text":"≥ 1.16.0, < 1.16.5","noFixRecorded":false,"fixedIn":null},{"text":"≥ 1.17.0, < 1.17.4","noFixRecorded":false,"fixedIn":null},{"text":"≥ 1.18.0, < 1.18.4","noFixRecorded":false,"fixedIn":null},{"text":"1.19.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 1.19.0, < 1.19.1 | ≥ 1.16.0, < 1.16.5 | ≥ 1.17.0, < 1.17.4 | ≥ 1.18.0, < 1.18.4 | 1.19.0","eol":{"isEol":true,"eolDate":"2022-07-13T00:00:00.000Z","matchMethod":"cpe","cycle":{"name":"1.19","label":"1.19","eolFrom":"2022-07-13T00:00:00.000Z","isLts":false,"isMaintained":false,"latestVersion":"1.19.5"},"product":{"name":"envoy","label":"Envoy","category":"server-app"}},"hubHref":"/vendor/envoyproxy/envoy"},{"vendor":"redhat","product":"servicemesh","name":"servicemesh","label":"servicemesh","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh","purlType":"rpm","versions":[{"text":"< 0:2.1.0-5.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-5.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-cni","name":"servicemesh-cni","label":"servicemesh-cni","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-cni","purlType":"rpm","versions":[{"text":"< 0:2.1.0-5.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-5.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-grafana","name":"servicemesh-grafana","label":"servicemesh-grafana","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-grafana","purlType":"rpm","versions":[{"text":"< 0:7.2.1-2.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:7.2.1-2.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-grafana-debuginfo","name":"servicemesh-grafana-debuginfo","label":"servicemesh-grafana-debuginfo","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-grafana-debuginfo","purlType":"rpm","versions":[{"text":"< 0:7.2.1-2.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:7.2.1-2.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-operator","name":"servicemesh-operator","label":"servicemesh-operator","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-operator","purlType":"rpm","versions":[{"text":"< 0:2.1.0-4.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-4.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-pilot-agent","name":"servicemesh-pilot-agent","label":"servicemesh-pilot-agent","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-pilot-agent","purlType":"rpm","versions":[{"text":"< 0:2.1.0-5.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-5.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-pilot-discovery","name":"servicemesh-pilot-discovery","label":"servicemesh-pilot-discovery","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-pilot-discovery","purlType":"rpm","versions":[{"text":"< 0:2.1.0-5.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-5.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-prometheus","name":"servicemesh-prometheus","label":"servicemesh-prometheus","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-prometheus","purlType":"rpm","versions":[{"text":"< 0:2.23.0-1.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.23.0-1.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-proxy","name":"servicemesh-proxy","label":"servicemesh-proxy","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-proxy","purlType":"rpm","versions":[{"text":"< 0:2.1.0-13.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-13.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-proxy-debuginfo","name":"servicemesh-proxy-debuginfo","label":"servicemesh-proxy-debuginfo","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-proxy-debuginfo","purlType":"rpm","versions":[{"text":"< 0:2.1.0-13.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-13.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-proxy-debugsource","name":"servicemesh-proxy-debugsource","label":"servicemesh-proxy-debugsource","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-proxy-debugsource","purlType":"rpm","versions":[{"text":"< 0:2.1.0-13.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-13.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-proxy-wasm","name":"servicemesh-proxy-wasm","label":"servicemesh-proxy-wasm","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-proxy-wasm","purlType":"rpm","versions":[{"text":"< 0:2.1.0-13.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-13.el8","eol":null,"hubHref":null},{"vendor":"redhat","product":"servicemesh-ratelimit","name":"servicemesh-ratelimit","label":"servicemesh-ratelimit","ecosystem":"Red Hat","cpePart":null,"purl":"pkg:rpm/redhat/servicemesh-ratelimit","purlType":"rpm","versions":[{"text":"< 0:2.1.0-1.el8","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 0:2.1.0-1.el8","eol":null,"hubHref":null}],"affectedCount":14,"eol":{"hasEol":true,"count":1},"references":[{"url":"https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history","label":"www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history","hostname":"www.envoyproxy.io","tags":["X Refsource MISC","Release Notes","Vendor Advisory"]},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chcc","label":"github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chcc","hostname":"github.com","tags":["X Refsource CONFIRM","Third Party Advisory"]},{"url":"https://access.redhat.com/errata/RHEA-2021:4051","label":"access.redhat.com/errata/RHEA-2021:4051","hostname":"access.redhat.com","tags":["Advisory"]},{"url":"https://issues.redhat.com/browse/MAISTRA-2693","label":"issues.redhat.com/browse/MAISTRA-2693","hostname":"issues.redhat.com","tags":["ARTICLE"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2021/rhea-2021_4051.json","label":"security.access.redhat.com/data/csaf/v2/advisories/2021/rhea-2021_4051.json","hostname":"security.access.redhat.com","tags":["Advisory"]},{"url":"https://access.redhat.com/security/cve/CVE-2021-32778","label":"access.redhat.com/security/cve/CVE-2021-32778","hostname":"access.redhat.com","tags":["REPORT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1996946","label":"bugzilla.redhat.com/show_bug.cgi?id=1996946","hostname":"bugzilla.redhat.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-32778","label":"www.cve.org/CVERecord?id=CVE-2021-32778","hostname":"www.cve.org","tags":["Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-32778","label":"nvd.nist.gov/vuln/detail/CVE-2021-32778","hostname":"nvd.nist.gov","tags":["Advisory"]},{"url":"https://istio.io/latest/news/security/istio-security-2021-008/","label":"istio.io/latest/news/security/istio-security-2021-008/","hostname":"istio.io","tags":["ARTICLE"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2021-08-24T20:30:11.000Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2024-08-03T23:33:55.854Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":30,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-20T04:06:21.043Z","stale":false,"partial":false}}