CVE-2021-4189

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2022-08-25. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 3%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
83.7%
KEV
Not listed

Published

August 24, 2022

Last Modified

December 17, 2025

References (19)

Vendor Advisories for CVE-2021-4189(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(7)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3.11-venv (3.11.0~rc1-1~22.04.1~esm1) @ jammy2026-05-25ubuntu
ubuntulibpython3.6 (3.6.9-1~18.04ubuntu1.7) @ bionic2026-05-25ubuntu
ubuntulibpython2.7-stdlib (2.7.6-8ubuntu0.6+esm12) @ trusty2026-05-25ubuntu
redhatpython3-0:3.6.8-45.el82022-05-10redhat
redhatpython27:2.7-8060020220210185952.8cdc22682022-05-10redhat
redhatpython27-python-0:2.7.18-4.el72022-05-02redhat
redhatrh-python38-python-urllib3-0:1.25.7-7.el72021-08-24redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(3)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 11× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-21 15:22 UTCEPSS rescore
  2. 2026-07-21 15:22 UTCEPSS rescore
  3. 2026-07-20 17:05 UTCEPSS rescore
  4. 2026-07-19 14:29 UTCEPSS rescore
  5. 2026-07-19 02:27 UTCEPSS rescore
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  7. 2026-07-18 10:02 UTCEPSS rescore
  8. 2026-07-16 21:20 UTCOSV refresh
  9. 2026-07-16 17:00 UTCEPSS rescore
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  11. 2026-07-15 16:55 UTCEPSS rescore
  12. 2026-07-15 01:58 UTCEPSS rescore
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  21. 2026-07-08 15:12 UTCEPSS rescore
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  24. 2026-07-06 16:25 UTCEPSS rescore
  25. 2026-07-06 16:25 UTCEPSS rescore
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  1. 2026-07-06 02:21 UTCEPSS rescore
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  3. 2026-07-05 02:28 UTCEPSS rescore
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  5. 2026-07-04 06:29 UTCEPSS rescore
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  7. 2026-07-01 15:04 UTCEPSS rescore
  8. 2026-06-30 23:20 UTCEPSS rescore
  9. 2026-06-29 14:04 UTCEPSS rescore
  10. 2026-06-29 14:04 UTCEPSS rescore
  11. 2026-06-28 20:02 UTCOSV refresh
  12. 2026-06-28 14:05 UTCEPSS rescore
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  15. 2026-06-27 03:07 UTCEPSS rescore
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  21. 2026-06-23 21:31 UTCEPSS rescore
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  23. 2026-06-22 14:24 UTCEPSS rescore
  24. 2026-06-21 14:55 UTCEPSS rescore
  25. 2026-06-21 01:58 UTCEPSS rescore
  26. 2026-06-21 01:58 UTCEPSS rescore
  27. 2026-06-19 19:24 UTCEPSS rescore
  28. 2026-06-19 19:24 UTCEPSS rescore
  29. 2026-06-18 17:51 UTCEPSS rescore
  30. 2026-06-18 17:51 UTCEPSS rescore
  31. 2026-06-17 17:51 UTCEPSS rescore
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  35. 2026-06-14 23:15 UTCEPSS rescore
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  37. 2026-06-13 22:58 UTCEPSS rescore
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  39. 2026-06-12 23:10 UTCEPSS rescore
  40. 2026-06-11 13:58 UTCEPSS rescore
  41. 2026-06-11 13:55 UTCOSV refresh
  42. 2026-06-10 22:16 UTCEPSS rescore
  43. 2026-06-10 13:20 UTCEPSS rescore
  44. 2026-06-08 14:15 UTCEPSS rescore
  45. 2026-06-08 14:15 UTCEPSS rescore
  46. 2026-06-08 14:15 UTCEPSS rescore
  47. 2026-06-07 15:23 UTCEPSS rescore
  48. 2026-06-07 15:23 UTCEPSS rescore
  49. 2026-06-06 13:46 UTCEPSS rescore
  50. 2026-06-06 13:46 UTCEPSS rescore
  51. 2026-06-05 22:45 UTCEPSS rescore
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  53. 2026-06-05 06:09 UTCEPSS rescore
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  55. 2026-06-04 13:11 UTCEPSS rescore
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  59. 2026-06-01 13:50 UTCEPSS rescore
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  61. 2026-05-31 22:29 UTCEPSS rescore
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  64. 2026-05-29 13:42 UTCEPSS rescore
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  67. 2026-05-27 13:39 UTCEPSS rescore
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  71. 2026-05-26 07:17 UTCEPSS rescore
  72. 2026-05-26 07:17 UTCEPSS rescore
  73. 2026-05-25 16:40 UTCEG score recompute
  74. 2026-05-25 16:40 UTCVendor advisory
  75. 2026-05-25 16:39 UTCGHSA enrichment

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Frequently asked(5)

What is CVE-2021-4189?
CVE-2021-4189 is a medium vulnerability published on August 24, 2022. 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…
When was CVE-2021-4189 disclosed?
CVE-2021-4189 was first published in the National Vulnerability Database on August 24, 2022, with the most recent update on December 17, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-4189 actively exploited?
CVE-2021-4189 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 83.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-4189?
CVE-2021-4189 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2021-4189?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-4189, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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