Envoy forwards early CONNECT data in TCP proxy mode
Description
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 packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/envoyproxy/envoyGo | >= 1.36.0, < 1.36.3 | 1.36.3 |
github.com/envoyproxy/envoyGo | >= 1.35.0, < 1.35.7 | 1.35.7 |
github.com/envoyproxy/envoyGo | >= 1.34.0, < 1.34.11 | 1.34.11 |
github.com/envoyproxy/envoyGo | < 1.33.13 | 1.33.13 |
Affected products
1- Range: >= 1.36.0, <= 1.36.2
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
3- github.com/advisories/GHSA-rj35-4m94-77jhghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2025-64763ghsaADVISORY
- github.com/envoyproxy/envoy/security/advisories/GHSA-rj35-4m94-77jhghsax_refsource_CONFIRMWEB
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