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HTTP Request Smuggling Affecting ecs-service-connect-agent package, versions <0:v1.39.1.0-1.amzn2023

Severity

 Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.46% (39th percentile)

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  • Snyk IDSNYK-AMZN2023-ECSSERVICECONNECTAGENT-19821442
  • published15 Sept 2026
  • disclosed21 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 15 Sep 2026

CVE-2026-73548  (opens in a new tab)
CWE-444  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 ecs-service-connect-agent to version 0:v1.39.1.0-1.amzn2023 or higher.
This issue was patched in ALAS2023-2026-2149.

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 an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.