Private-network service probing via trusted PASV host
Published Dec 3, 2022 · Updated Apr 24, 2025
SSRF in Apache Commons Net before 3.9.0 allows remote attackers to probe private-network services through a malicious FTP server. FTPClient._parsePassiveModeReply accepts the PASV reply's IP address as the data-channel host instead of retaining the control connection's peer. Exploitation requires an application to connect to the attacker-controlled FTP server and enter passive mode; the resulting connections disclose information about reachable internal services.
Summary
What happened
SSRF in Apache Commons Net before 3.9.0 allows remote attackers to probe private-network services through a malicious FTP server. FTPClient._parsePassiveModeReply accepts the PASV reply's IP address as the data-channel host instead of retaining the control connection's peer. Exploitation requires an application to connect to the attacker-controlled FTP server and enter passive mode; the resulting connections disclose information about reachable internal services.
The record
- CVE
- CVE-2021-37533
- Published
- Dec 3, 2022
- Updated
- Apr 24, 2025
- Vendor
- The Apache Software Foundation
- Product
- Apache Commons Net
- Classifications
- CWE-20, T1046
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 3, 2022CVE publishedPublication date reported by the CVE source.
- Apr 24, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=Apache Commons Net <3.9.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
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Your stack
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