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    CVE-2021-3733

    There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.

    Published:Aug 10, 2021
    Last Modified:Nov 3, 2025
    EPS:Mar 7, 2022
    EPSS Score:0.00675
    CVSS Score:6.5

    Affected Products

    Vendor
    Fedoraproject
    Product
    Extra Packages For Enterprise Linux
    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Netapp
    Product
    Hci Compute Node Firmware
    Vendor
    Netapp
    Product
    Management Services For Element Software And Netapp Hci
    Vendor
    Netapp
    Product
    Ontap Select Deploy Administration Utility
    Vendor
    Netapp
    Product
    Solidfire\, Enterprise Sds \& Hci Storage Node
    Vendor
    Python
    Product
    Python
    Vendor
    Redhat
    Product
    Codeready Linux Builder
    Vendor
    Redhat
    Product
    Codeready Linux Builder For Ibm Z Systems
    Vendor
    Redhat
    Product
    Codeready Linux Builder For Power Little Endian
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Enterprise Linux Eus
    Vendor
    Redhat
    Product
    Enterprise Linux For Ibm Z Systems
    Vendor
    Redhat
    Product
    Enterprise Linux For Ibm Z Systems Eus
    Vendor
    Redhat
    Product
    Enterprise Linux For Power Little Endian
    Vendor
    Redhat
    Product
    Enterprise Linux For Power Little Endian Eus
    Vendor
    Redhat
    Product
    Enterprise Linux Server Aus
    Vendor
    Redhat
    Product
    Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions
    Vendor
    Redhat
    Product
    Enterprise Linux Server Tus
    Vendor
    Redhat
    Product
    Enterprise Linux Server Update Services For Sap Solutions
    Vendor
    Redhat
    Product
    Rhel Software Collections

    Exploits

    https://bugs.python.org/issue43075https://bugs.python.org/issue43075

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    References

    https://bugs.python.org/issue43075
    https://bugzilla.redhat.com/show_bug.cgi?id=1995234
    https://github.com/python/cpython/commit/7215d1ae25525c92b026166f9d5cac85fb
    https://github.com/python/cpython/pull/24391
    https://lists.debian.org/debian-lts-announce/2023/05/msg00024.html
    https://lists.debian.org/debian-lts-announce/2023/06/msg00039.html
    https://security.netapp.com/advisory/ntap-20220407-0001/
    https://ubuntu.com/security/CVE-2021-3733
    https://bugs.python.org/issue43075
    https://bugzilla.redhat.com/show_bug.cgi?id=1995234
    https://github.com/python/cpython/commit/7215d1ae25525c92b026166f9d5cac85fb
    https://github.com/python/cpython/pull/24391
    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://security.netapp.com/advisory/ntap-20220407-0001/
    https://ubuntu.com/security/CVE-2021-3733

    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