CVE-2025-64763 — Envoy forwards early CONNECT data in TCP proxy mode

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
envoyproxy / envoy	affected >= 1.36.0, <= 1.36.2; affected >= 1.35.0, <= 1.35.6; affected >= 1.34.0, <= 1.34.10; affected <= 1.33.12

CWE

CWE-693

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-rj35-4m94-77jh

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.