Indexing blockage via malformed data sent through S2S or HEC protocols in Splunk Enterprise

In Splunk Enterprise versions below 8.2.9, 8.1.12, and 9.0.2, sending a malformed file through the Splunk-to-Splunk (S2S) or HTTP Event Collector (HEC) protocols to an indexer results in a blockage or denial-of-service preventing further indexing.