What is CVE-2021-20333?

CVE-2021-20333 is a medium-severity vulnerability in MongoDB, classified under Improper Output Neutralization for Logs. CVSS score: 5.3/10. Published 2021-07-23.

How severe is CVE-2021-20333?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in MongoDB

CVE-2021-20333

Sending specially crafted commands to a MongoDB Server may result in artificial log entries being generated or for log entries to be split. This issue affects MongoDB Server v3.6 versions prior to 3.6.20; MongoDB Server v4.0 versions prior to 4.0.21 and MongoDB Server v4.2 versions prior to 4.2.10.

Published 2021-07-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.013 (69.0th percentile), scored 2026-10-01.

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 69.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: +0.000

Affected products

MongoDB
MongoDB Inc. Server — versions 3.6, 4.0, 4.2

Weakness classification (CWE)

References

jira.mongodb.org/browse/SERVER-50605 (Exploit, Patch, Vendor Advisory)

Frequently asked questions

What is CVE-2021-20333?: CVE-2021-20333 is a medium-severity vulnerability in MongoDB, classified under Improper Output Neutralization for Logs. CVSS score: 5.3/10. Published 2021-07-23.
How severe is CVE-2021-20333?: Medium severity. CVSS v3 base score is 5.3 out of 10.