CVE-2021-20330

Name: CVE-2021-20330
Creator: NVD / NIST
Published: 2021-12-15T13:15:07.633+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.04%

Last modified Jun 17, 2026

CVE-2021-20330 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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.. EPSS estimates a 1.04% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.04%

59.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Mongodb	Mongodb	>= 4.0.0, < 4.0.25
Mongodb	Mongodb	>= 4.2.0, < 4.2.14
Mongodb	Mongodb	>= 4.4.0, < 4.4.6

References

https://jira.mongodb.org/browse/SERVER-36263Issue Tracking, Patch, Vendor Advisory
https://jira.mongodb.org/browse/SERVER-36263Issue Tracking, Patch, Vendor Advisory

Timeline

Published: Dec 15, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20330?

How severe is CVE-2021-20330?

CVE-2021-20330 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.04% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20330?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20330?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST