Protection Mechanism Failure Affecting ecs-service-connect-agent package, versions <0:v1.34.4.2-1.amzn2023


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.31% (23rd percentile)

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  • Snyk IDSNYK-AMZN2023-ECSSERVICECONNECTAGENT-14905183
  • published9 Jan 2026
  • disclosed3 Dec 2025

Introduced: 3 Dec 2025

CVE-2025-64763  (opens in a new tab)
CWE-693  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 ecs-service-connect-agent to version 0:v1.34.4.2-1.amzn2023 or higher.
This issue was patched in ALAS2023-2025-1357.

NVD Description

Note: Versions mentioned in the description apply only to the upstream ecs-service-connect-agent package and not the ecs-service-connect-agent package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1