CVE-2021-43826: Envoyproxy Envoy

High severity, CVSS 7.5. EPSS: 1.1% chance of exploitation in the next 30 days.

Envoy is an open source edge and service proxy, designed for cloud-native applications. In affected versions of Envoy a crash occurs when configured for :ref:`upstream tunneling <envoy_v3_api_field_extensions.filters.network.tcp_proxy.v3.TcpProxy.tunneling_config>` and the downstream connection disconnects while the the upstream connection or http/2 stream is still being established. There are no workarounds for this issue. Users are advised to upgrade.

Affected products

• Envoyproxy Envoy: before 1.18.6 (fixed in 1.18.6); from 1.19.0, before 1.19.3 (fixed in 1.19.3); from 1.20.0, before 1.20.2 (fixed in 1.20.2); from 1.21.0, before 1.21.1 (fixed in 1.21.1)

Published 2022-02-22. Last modified 2026-06-17.