envoyproxy/envoy

Stateful Session cookies incompatible between Envoy Processes.

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Aperta il 25 mar 2026

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bughelp wanted

Descrizione

Title: Stateful Session cookies incompatible between Envoy Processes.

Description: When using Envoy as an Edge Proxy with multiple instances (an NLB in front) AND using the StatefulSession with cookies doesn't work properly.

The cookie is encoded with the expiry time BUT it uses the monotonic clock:

https://github.com/envoyproxy/envoy/blob/21b70d126c0a5c16d844658ee2db68f94deb7548/source/extensions/http/stateful_session/cookie/cookie.cc#L21-L22

When HTTP requests are routed to different Envoy processes, they will have different values for their monotonic clock and the cookie can inadvertently expire sooner then its should, which will cause a new backend to get selected.

I believe the appropriate fix is for time_source_.systemTime() to be used so that two envoy processes can validate each other cookies.

cc @cpakulski

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