For those that may try to search for this bug in the future, the error I received was
Error 411: gth required
The issue is that libmicrohttpd exhibits a bug when Content-Length is omitted, even if Transfer-Encoding is set to "chunked". The HTTP/1.1 spec allows Content-Length to be omitted when the length is unknown as long as Transfer-Encoding: Chunked is specified. The proper behavior would be for journald to return an error to the client when it has received too much data.
For those that may try to search for this bug in the future, the error I received was
Error 411: gth required
The issue is that libmicrohttpd exhibits a bug when Content-Length is omitted, even if Transfer-Encoding is set to "chunked". The HTTP/1.1 spec allows Content-Length to be omitted when the length is unknown as long as Transfer-Encoding: Chunked is specified. The proper behavior would be for journald to return an error to the client when it has received too much data.