●Change8

Migrating to Envoy v1.38.1

Version v1.38.1 introduces 1 breaking change. This guide details how to update your code.

Released: 6/4/2026

1
Breaking Changes
2
Migration Steps
5
Affected Symbols

⚠️ Check Your Code

If you use any of these symbols, you need to read this guide:

http2oauth2dynamic_modulesrouterupstream

Breaking Changes

●Issue #1

The upstream transport failure reason is no longer included in the HTTP response body sent to downstream clients. To restore this behavior, enable the runtime feature ``envoy.reloadable_features.hide_transport_failure_reason_in_response_body``.

Migration Steps

  1. 1
    If you relied on the upstream transport failure reason being present in the HTTP response body, you must enable the runtime feature ``envoy.reloadable_features.hide_transport_failure_reason_in_response_body`` to restore the previous behavior.
  2. 2
    If you wish to re-enable automatic coalescing of load balancer rebuilds during EDS batch updates, enable the runtime feature ``envoy.reloadable_features.coalesce_lb_rebuilds_on_batch_update``.

Release Summary

This release focuses heavily on security fixes, addressing vulnerabilities in HTTP/2 header limits, HMAC verification, and AES-CBC decryption. It also includes several bug fixes and minor behavior changes regarding upstream failure reasons and load balancer rebuild coalescing.

Need More Details?

View the full release notes and all changes for Envoy v1.38.1.

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