MongoDB 3.4.x before 3.4.10, and 3.5.x-development, has a disabled-by-default configuration setting, networkMessageCompressors (aka wire protocol compression), which exposes a vulnerability when enabled that could be exploited by a malicious attacker to deny service or modify memory.

An unprivileged user or program on Microsoft Windows which can create OpenSSL configuration files in a fixed location may cause utility programs shipped with MongoDB server to run attacker defined code as the user running the utility. This issue affects: MongoDB Inc. MongoDB Server 4.0 prior to 4.0.11; 3.6 prior to 3.6.14; 3.4 prior to 3.4.22.

After user deletion in MongoDB Server the improper invalidation of authorization sessions allows an authenticated user's session to persist and become conflated with new accounts, if those accounts reuse the names of deleted ones. This issue affects MongoDB Server v4.0 versions prior to 4.0.9; MongoDB Server v3.6 versions prior to 3.6.13 and MongoDB Server v3.4 versions prior to 3.4.22.

Workaround: After deleting one or more users, restart any nodes which may have had active user authorization sessions.

Refrain from creating user accounts with the same name as previously deleted accounts.