What is CVE-2021-37533?

CVE-2021-37533 is a medium-severity improper input validation vulnerability in commons-net:commons-net (maven), affecting versions < 3.9.0. It is fixed in 3.9.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.

How severe is CVE-2021-37533?

CVE-2021-37533 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of commons-net:commons-net are affected by CVE-2021-37533?

commons-net:commons-net (maven) versions < 3.9.0 is affected.

Is there a fix for CVE-2021-37533?

Yes. CVE-2021-37533 is fixed in 3.9.0. Upgrade to this version or later.

Is CVE-2021-37533 exploitable, and should I be worried?

Whether CVE-2021-37533 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2021-37533 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2021-37533 in commons-net:commons-net

Q: How severe is CVE-2021-37533?

CVE-2021-37533 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of commons-net:commons-net are affected by CVE-2021-37533?

commons-net:commons-net (maven) versions < 3.9.0 is affected.

Q: Is there a fix for CVE-2021-37533?

Yes. CVE-2021-37533 is fixed in 3.9.0. Upgrade to this version or later.

Q: Is CVE-2021-37533 exploitable, and should I be worried?

Whether CVE-2021-37533 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2021-37533 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2021-37533?

Upgrade commons-net:commons-net to 3.9.0 or later.

Summary

Apache Commons Net vulnerable to information leakage via malicious server

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.

Impact

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2021-37533 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.9.0); upgrading removes the vulnerable code path.

Affected versions

commons-net:commons-net (< 3.9.0)

Security releases

commons-net:commons-net → 3.9.0 (maven)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade commons-net:commons-net to 3.9.0 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2021-37533? CVE-2021-37533 is a medium-severity improper input validation vulnerability in commons-net:commons-net (maven), affecting versions < 3.9.0. It is fixed in 3.9.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
How severe is CVE-2021-37533? CVE-2021-37533 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of commons-net:commons-net are affected by CVE-2021-37533? commons-net:commons-net (maven) versions < 3.9.0 is affected.
Is there a fix for CVE-2021-37533? Yes. CVE-2021-37533 is fixed in 3.9.0. Upgrade to this version or later.
Is CVE-2021-37533 exploitable, and should I be worried? Whether CVE-2021-37533 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2021-37533 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2021-37533? Upgrade commons-net:commons-net to 3.9.0 or later.