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pypy3 — security advisory

Type: advisorySources: OSVAdvisory ID: DEBIAN-CVE-2021-4189

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.

Products
pypy3
Affected versions
Not specified
Fixed versions
7.3.5+dfsg-2
CVEs
CVE-2021-4189
Confirmed fixed CVEs
Not specified
Updated in this feed
30 Oct 2026, 16:48 UTC · Revision 1

Source evidence

DEBIAN-CVE-2021-4189

core-osv · Original source

Published 24 Aug 2022, 16:15 UTC

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.

osv:DEBIAN-CVE-2021-4189

pypy3

Fixed versions: 7.3.5+dfsg-2

pypy3

Fixed versions: 7.3.5+dfsg-2

pypy3

Fixed versions: 7.3.5+dfsg-2

Complete source record
{
  "id": "4b0137182d3575d75cd218d762693d06ae2c9eaca79e5bd3b367ff53385c7503",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2021-4189",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2021-4189",
    "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.",
    "evidence": "osv:DEBIAN-CVE-2021-4189",
    "products": [
      {
        "name": {
          "value": "pypy3",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.3.5+dfsg-2",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "pypy3",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.3.5+dfsg-2",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "pypy3",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.3.5+dfsg-2",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2021-4189",
      "aliases": [
        "DEBIAN-CVE-2021-4189"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7.3.5+dfsg-2"
                }
              ]
            }
          ],
          "package": {
            "name": "pypy3",
            "purl": "pkg:deb/debian/pypy3?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4189.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7.3.5+dfsg-2"
                }
              ]
            }
          ],
          "package": {
            "name": "pypy3",
            "purl": "pkg:deb/debian/pypy3?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4189.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "7.3.5+dfsg-2"
                }
              ]
            }
          ],
          "package": {
            "name": "pypy3",
            "purl": "pkg:deb/debian/pypy3?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4189.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-15T09:47:40.336446707Z",
      "provider": "osv",
      "upstream": [
        "CVE-2021-4189"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2021-4189"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2021-4189",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 328259,
  "published_at": "2022-08-24T16:15:09.827+00:00"
}