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 products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| envoyproxy | envoy | >= 1.36.0, <= 1.36.2, >= 1.35.0, <= 1.35.6, >= 1.34.0, <= 1.34.10, <= 1.33.12 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | ecs-service-connect-agent | v1.34.4.2-1.amzn2023 | ALAS2023-2025-1357 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/envoyproxy/envoy | >= 1.36.0, < 1.36.3 | 1.36.3 | GHSA-rj35-4m94-77jh |
| Go | github.com/envoyproxy/envoy | >= 1.35.0, < 1.35.7 | 1.35.7 | GHSA-rj35-4m94-77jh |
| Go | github.com/envoyproxy/envoy | >= 1.34.0, < 1.34.11 | 1.34.11 | GHSA-rj35-4m94-77jh |
| Go | github.com/envoyproxy/envoy | < 1.33.13 | 1.33.13 | GHSA-rj35-4m94-77jh |
Advisories 1
- ALAS2023-2025-1357 Important: ecs-service-connect-agent security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Jan 7, 2026