CVE-2021-4189 (GCVE-0-2021-4189)

Vulnerability from cvelistv5 – Published: 2022-08-24 00:00 – Updated: 2025-12-17 21:36
VLAI
Summary
A flaw was found in Python, specifically in the FTP (File Transfer Protocol) client library in PASV (passive) mode. The issue is how the FTP client trusts the host from the PASV response by default. This flaw allows an attacker to set up a malicious FTP server that can trick FTP clients into connecting back to a given IP address and port. This vulnerability could lead to FTP client scanning ports, which otherwise would not have been possible.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-06-25 14:59 UTC
CWE
  • Not-Known
  • CWE-252 - Unchecked Return Value
Assigner
References
Impacted products
Vendor Product Version
n/a python Affected: Fixed in python 3.6.14, python 3.7.11, python 3.8.9, python 3.9.3, python 3.10.0
Show details on NVD website
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      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-28T07:49:05+00:00",
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      "initial_release_date": "2021-12-21T00:00:00+00:00",
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      "product_status:known_affected": "23",
      "product_status:known_not_affected": "168",
      "source": "Red Hat CSAF VEX",
      "status": "final",
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      "version": "3"
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      "current_release_date": "2026-08-12T00:25:59Z",
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      "initial_release_date": "2023-02-15T03:47:47Z",
      "product_status:known_affected": "396",
      "product_status:known_not_affected": "311",
      "product_status:recommended": "619",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-4189",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-4189.json",
      "version": "50"
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  }
}



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Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.