CVE-2023-27493: Envoyproxy Envoy

Critical severity, CVSS 9.1. EPSS: 0.5% chance of exploitation in the next 30 days.

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, Envoy does not sanitize or escape request properties when generating request headers. This can lead to characters that are illegal in header values to be sent to the upstream service. In the worst case, it can cause upstream service to interpret the original request as two pipelined requests, possibly bypassing the intent of Envoy’s security policy. Versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9 contain a patch. As a workaround, disable adding request headers based on the downstream request properties, such as downstream certificate properties.

Affected products

• Envoyproxy Envoy: before 1.22.9 (fixed in 1.22.9); from 1.23.0, before 1.23.6 (fixed in 1.23.6); from 1.24.0, before 1.24.4 (fixed in 1.24.4); from 1.25.0, before 1.25.3 (fixed in 1.25.3)

Published 2023-04-04. Last modified 2026-06-17.