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    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.

    Published:Dec 21, 2021
    Last Modified:Dec 17, 2025
    EPS:Aug 24, 2022
    EPSS Score:0.00302
    CVSS Score:5.3

    Affected Products

    Vendor
    Debian
    Product
    Debian Linux
    Vendor
    Netapp
    Product
    Ontap Select Deploy Administration Utility
    Vendor
    Python
    Product
    Python
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Rhel Software Collections
    Vendor
    Redhat
    Product
    Software Collections

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-252 Unchecked Return Value

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

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    References

    https://access.redhat.com/security/cve/CVE-2021-4189
    https://bugs.python.org/issue43285
    https://bugzilla.redhat.com/show_bug.cgi?id=2036020
    https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
    https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
    https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
    https://python-security.readthedocs.io/vuln/ftplib-pasv.html
    https://security-tracker.debian.org/tracker/CVE-2021-4189
    https://security.netapp.com/advisory/ntap-20221104-0004/
    https://access.redhat.com/security/cve/CVE-2021-4189
    https://bugs.python.org/issue43285
    https://bugzilla.redhat.com/show_bug.cgi?id=2036020
    https://github.com/python/cpython/commit/0ab152c6b5d95caa2dc1a30fa96e10258b5f188e
    https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
    https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
    https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html
    https://python-security.readthedocs.io/vuln/ftplib-pasv.html
    https://security-tracker.debian.org/tracker/CVE-2021-4189
    https://security.netapp.com/advisory/ntap-20221104-0004/

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High