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.

• CWE-834
• CWE-834

• https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chccThird Party Advisory
• https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_historyRelease Notes, Vendor Advisory
• https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chccThird Party Advisory
• https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_historyRelease Notes, Vendor Advisory

Published

Aug 24, 2021

Last Modified

Jun 17, 2026

Status

Modified

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