CVE-2021-43825: Envoyproxy Envoy

High severity, CVSS 7.5. EPSS: 0.9% chance of exploitation in the next 30 days.

Envoy is an open source edge and service proxy, designed for cloud-native applications. Sending a locally generated response must stop further processing of request or response data. Envoy tracks the amount of buffered request and response data and aborts the request if the amount of buffered data is over the limit by sending 413 or 500 responses. However when the buffer overflows while response is processed by the filter chain the operation may not be aborted correctly and result in accessing a freed memory block. If this happens Envoy will crash resulting in a denial of service.

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.