CVE-2024-23326: Envoyproxy Envoy

High severity, CVSS 8.2. EPSS: 0.4% chance of exploitation in the next 30 days.

Envoy is a cloud-native, open source edge and service proxy. A theoretical request smuggling vulnerability exists through Envoy if a server can be tricked into adding an upgrade header into a response. Per RFC https://www.rfc-editor.org/rfc/rfc7230#section-6.7 a server sends 101 when switching protocols. Envoy incorrectly accepts a 200 response from a server when requesting a protocol upgrade, but 200 does not indicate protocol switch. This opens up the possibility of request smuggling through Envoy if the server can be tricked into adding the upgrade header to the response.

Affected products

• Envoyproxy Envoy: before 1.27.6 (fixed in 1.27.6); from 1.28.0, before 1.28.4 (fixed in 1.28.4); from 1.29.0, before 1.29.5 (fixed in 1.29.5); from 1.30.0, before 1.30.2 (fixed in 1.30.2)

Published 2024-06-04. Last modified 2026-06-17.