Is CVE-2021-37533 in the CISA KEV catalog?

No. CVE-2021-37533 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-37533?

CVE-2021-37533 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2021-37533?

CVE-2021-37533 has an EPSS score of 1.86% (77th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-37533?

Upgrade libcommons-net-java on debian 11 to 3.6-1+deb11u1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2021-37533

MEDIUMEPSS 77th pctl

6.5

CVSS v3

NVD

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.

CWE-20Improper Input Validation

How to fix

Remediation Available

libcommons-net-javaDebian

Fixed in:3.6-1+deb11u1CVE-2021-37533

Fixed in:3.9.0-1CVE-2021-37533

libcommons-net-javaUbuntu

Fixed in:3.4-2ubuntu2+esm1USN-6037-1

Fixed in:3.6-1+deb11u1build0.18.04.1USN-6037-1

Fixed in:3.6-1+deb11u1build0.20.04.1USN-6037-1

Fixed in:3.6-1+deb11u1build0.22.04.1USN-6037-1

Fixed in:3.6-1+deb11u1build0.22.10.1USN-6037-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

1.86%probability of exploitation in 30 days

77thpercentile

Elevated risk: more likely to be exploited than 77% of all known CVEs.

References

Vendor Advisory1

lists.apache.org

Third-Party Advisory3

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-04-24.