CVE-2025-64763
December 03, 2025
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
https://github.com/envoyproxy/envoy.git (GITHUB):
Affected version(s) >=v1.0.0 <v1.33.13Fix Suggestion:
Update to version v1.33.13https://github.com/envoyproxy/envoy.git (GITHUB):
Affected version(s) >=v1.34.0 <v1.34.11Fix Suggestion:
Update to version v1.34.11https://github.com/envoyproxy/envoy.git (GITHUB):
Affected version(s) >=v1.36.0 <v1.36.3Fix Suggestion:
Update to version v1.36.3https://github.com/envoyproxy/envoy.git (GITHUB):
Affected version(s) >=v1.35.0 <v1.35.7Fix Suggestion:
Update to version v1.35.7github.com/envoyproxy/envoy (GO):
Affected version(s) >=v1.34.0 <v1.34.11Fix Suggestion:
Update to version v1.34.11github.com/envoyproxy/envoy (GO):
Affected version(s) >=v1.36.0 <v1.36.3Fix Suggestion:
Update to version v1.36.3github.com/envoyproxy/envoy (GO):
Affected version(s) >=v1.35.0 <v1.35.7Fix Suggestion:
Update to version v1.35.7Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.3
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
3.7
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Protection Mechanism Failure
