Connection reset on "payload too large" (413) response from target server

[mdmower-csnw]

When a user attempts to upload a file and the target server responds with HTTP status 413 (payload too large) before reading the entire request body, the proxy often causes "connection reset" instead of forwarding the response to the user.

I observed this while proxying an IIS site but was able to create a minimal reproduction using an express server as well. See repo Proxy connection reset on content too big for code and reproduction steps.

I've reproduced this in Chrome and Firefox on Windows.

Expected result:

Actual result: