CVE-2019-12401

Solr versions 1.3.0 to 1.4.1, 3.1.0 to 3.6.2 and 4.0.0 to 4.10.4 are vulnerable to an XML resource consumption attack (a.k.a. Lol Bomb) via it?s update handler.?By leveraging XML DOCTYPE and ENTITY type elements, the attacker can create a pattern that will expand when the server parses the XML causing OOMs.

Source: CVE-2019-12401