CVE-2019-2393
A user authorized to perform database queries may trigger denial of service by issuing specially crafted queries, which use $lookup and collations. This issue affects: MongoDB Inc. MongoDB Server v4.2 versions prior to 4.2.1; v4.0 versions prior to 4.0.13; v3.6 versions prior to 3.6.15.
Source: CVE-2019-2393