Envoy Proxy Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling) Vulnerability - CVE-2026-48743 - Vulnerability Database

Envoy Proxy

Envoy Proxy Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling) Vulnerability - CVE-2026-48743

High

Reference: CVE-2026-48743

NVD Link: https://nvd.nist.gov/vuln/detail/CVE-2026-48743

Title: Envoy Proxy Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling) Vulnerability

Overview:

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11 1.36.7 1.37.3 and 1.38.1 Envoy can translate a downstream HTTP/3 request that is complete at the transport layer (HEADERS with FIN / headers-only close) but still carries a nonzero Content-Length into a complete upstream HTTP/1 request with unresolved body debt. In an HTTP/1 upstream deployment where the origin replies before reading the declared body and keeps the connection reusable the beginning of the next Envoy-generated upstream request can be consumed as the first request39s body. The remaining bytes are then parsed by the origin as a new HTTP/1 request. This was reproduced as a route-bypass/desync: direct /pwn was denied by Envoy but the second downstream H3 stream received the response for backend-parsed GET /pwn HTTP/1.1. This vulnerability is fixed in 1.35.11 1.36.7 1.37.3 and 1.38.1.