Graylog is a free and open log management platform. Starting with 6.1, HTTP Inputs can be configured to check if a specified header is present and has a specified value to authenticate HTTP-based ingestion. Unfortunately, even though in cases of a missing header or a wrong value the correct HTTP response (401) is returned, the message will be ingested nonetheless. To mitigate the vulnerability, disable http-based inputs and allow only authenticated pull-based inputs. This vulnerability is fixed in 6.1.9.
https://github.com/Graylog2/graylog2-server/security/advisories/GHSA-q7g5-jq6p-6wvx
https://github.com/Graylog2/graylog2-server/commit/31bc13d3cd6f550ec83473d0f8666cd3ebf50f10