CVE-2025-64763

Summary

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 Software

VendorProductVersion RangeStatus
envoyproxyenvoy>= 1.36.0, <= 1.36.2affected
envoyproxyenvoy>= 1.35.0, <= 1.35.6affected
envoyproxyenvoy>= 1.34.0, <= 1.34.10affected
envoyproxyenvoy<= 1.33.12affected

Weaknesses

  • CWE-693: CWE-693: Protection Mechanism Failure

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References