CVE-2021-37533

Name: CVE-2021-37533
Creator: NVD / NIST
Published: 2022-12-03T15:15:09.747+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.86%

Last modified Jun 17, 2026

CVE-2021-37533 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. Prior to Apache Commons Net 3.9.0, Net's FTP client trusts the host from PASV response by default. A malicious server can redirect the Commons Net code to use a different host, but the user has to connect to the malicious server in the first place. EPSS estimates a 1.86% chance of exploitation in the next 30 days.

Description

Prior to Apache Commons Net 3.9.0, Net's FTP client trusts the host from PASV response by default. A malicious server can redirect the Commons Net code to use a different host, but the user has to connect to the malicious server in the first place. This may lead to leakage of information about services running on the private network of the client. The default in version 3.9.0 is now false to ignore such hosts, as cURL does. See https://issues.apache.org/jira/browse/NET-711.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.86%

76.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Apache	Commons Net	< 3.9.0
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0

References

http://www.openwall.com/lists/oss-security/2022/12/03/1Issue Tracking, Mailing List, Third Party Advisory
https://lists.apache.org/thread/o6yn9r9x6s94v97264hmgol1sf48mvx7Issue Tracking, Mailing List, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00038.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5307Third Party Advisory
http://www.openwall.com/lists/oss-security/2022/12/03/1Issue Tracking, Mailing List, Third Party Advisory
https://lists.apache.org/thread/o6yn9r9x6s94v97264hmgol1sf48mvx7Issue Tracking, Mailing List, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00038.htmlMailing List, Third Party Advisory
https://www.debian.org/security/2022/dsa-5307Third Party Advisory

Timeline

Published: Dec 3, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-37533?

How severe is CVE-2021-37533?

CVE-2021-37533 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.86% probability of exploitation in the next 30 days.

How do I fix CVE-2021-37533?

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-2021-37533?

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

Scan your code now

Source: NVD / NIST