CVE-2021-39204: Envoyproxy Envoy

High severity, CVSS 7.5. EPSS: 1.7% chance of exploitation in the next 30 days.

Pomerium is an open source identity-aware access proxy. Envoy, which Pomerium is based on, incorrectly handles resetting of HTTP/2 streams with excessive complexity. This can lead to high CPU utilization when a large number of streams are reset. This can result in a DoS condition. Pomerium versions 0.14.8 and 0.15.1 contain an upgraded envoy binary with this vulnerability patched.

Affected products

• Envoyproxy Envoy: up to and including 1.16.4; from 1.17.0, before 1.17.4 (fixed in 1.17.4); from 1.18.0, before 1.18.4 (fixed in 1.18.4); version 1.19.0 only
• Pomerium Pomerium: before 0.14.8 (fixed in 0.14.8); version 0.15.0 only

Published 2021-09-09. Last modified 2026-06-17.