CVE-2021-20330: MongoDB

Medium severity, CVSS 6.5. EPSS: 1.1% chance of exploitation in the next 30 days.

An attacker with basic CRUD permissions on a replicated collection can run the applyOps command with specially malformed oplog entries, resulting in a potential denial of service on secondaries. This issue affects MongoDB Server v4.0 versions prior to 4.0.27; MongoDB Server v4.2 versions prior to 4.2.16; MongoDB Server v4.4 versions prior to 4.4.9.

Affected products

• MongoDB MongoDB: from 4.0.0, before 4.0.25 (fixed in 4.0.25); from 4.2.0, before 4.2.14 (fixed in 4.2.14); from 4.4.0, before 4.4.6 (fixed in 4.4.6)

Published 2021-12-15. Last modified 2026-06-17.