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Envoy Proxy Protection Mechanism Failure Vulnerability - CVE-2025-64763 - Vulnerability Database
Envoy Proxy

Envoy Proxy Protection Mechanism Failure Vulnerability - CVE-2025-64763

Medium
Reference: CVE-2025-64763
NVD Link: https://nvd.nist.gov/vuln/detail/CVE-2025-64763
Title: Envoy Proxy Protection Mechanism Failure Vulnerability
Overview:

Envoy is a high-performance edge/middle/service proxy. In 1.33.12 1.34.10 1.35.6 1.36.2 and earlier when Envoy is configured in TCP proxy mode to handle CONNECT requests it accepts client data before issuing a 2xx response and forwards that data to the upstream TCP connection. If a forwarding proxy upstream from Envoy then responds with a non-2xx status this can cause a de-synchronized CONNECT tunnel state. By default Envoy continues to allow early CONNECT data to avoid disrupting existing deployments. The envoy.reloadable_features.reject_early_connect_data runtime flag can be set to reject CONNECT requests that send data before a 2xx response when intermediaries upstream from Envoy may reject establishment of a CONNECT tunnel.