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    CVE-2021-3737

    A flaw was found in python. An improperly handled HTTP response in the HTTP client code of python may allow a remote attacker, who controls the HTTP server, to make the client script enter an infinite loop, consuming CPU time. The highest threat from this vulnerability is to system availability.

    Published:Aug 9, 2021
    Last Modified:Dec 17, 2025
    EPS:Mar 4, 2022
    EPSS Score:0.00243
    CVSS Score:7.5

    Affected Products

    Vendor
    Canonical
    Product
    Ubuntu Linux
    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Netapp
    Product
    Hci
    Vendor
    Netapp
    Product
    Management Services For Element Software
    Vendor
    Netapp
    Product
    Netapp Xcp Smb
    Vendor
    Netapp
    Product
    Ontap Select Deploy Administration Utility
    Vendor
    Netapp
    Product
    Xcp Nfs
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Binding Support Function
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Network Exposure Function
    Vendor
    Oracle
    Product
    Communications Cloud Native Core Policy
    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 For Ibm Z Systems
    Vendor
    Redhat
    Product
    Enterprise Linux For Power Little Endian
    Vendor
    Redhat
    Product
    Rhel Software Collections

    Exploits

    https://bugs.python.org/issue44022https://bugs.python.org/issue44022

    Related CVEs

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    CVE-2026-47337 (CVSS 3.3) — Ubuntu Linux 6.8, 6.17 and 7.0 contain SAUCE patches with a possible NULL pointer dereference in the handling …
    CVE-2026-47336 (CVSS 3.3) — Ubuntu Linux 6.8 contains SAUCE patches with a possible use of an uninitialized variable in AppArmor AF_INET/A…
    CVE-2026-47335 (CVSS 5.5) — Ubuntu Linux 6.8 contains SAUCE patches with a possible NULL pointer dereference in the handling of AppArmor n…
    CVE-2026-47334 (CVSS 5.5) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly sleep while holding a spinlock…
    CVE-2026-47333 (CVSS 7.8) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which can potentially incorrectly compute the si…
    CVE-2026-47332 (CVSS 5.5) — Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly validate the size of an intern…
    CVE-2026-47331 (CVSS 7.8) — Ubuntu Linux 6.8 contains AppArmor SAUCE patches which fail to acquire a lock when modifying a linked list. An…
    CVE-2026-47330 (CVSS 3.3) — Ubuntu Linux 6.8, 7.17 and 7.0 contain AppArmor SAUCE patches which can, under certain circumstances, use an u…

    References

    https://bugs.python.org/issue44022
    https://bugzilla.redhat.com/show_bug.cgi?id=1995162
    https://github.com/python/cpython/pull/25916
    https://github.com/python/cpython/pull/26503
    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/urllib-100-continue-loop.html
    https://security.netapp.com/advisory/ntap-20220407-0009/
    https://ubuntu.com/security/CVE-2021-3737
    https://www.oracle.com/security-alerts/cpujul2022.html
    https://bugs.python.org/issue44022
    https://bugzilla.redhat.com/show_bug.cgi?id=1995162
    https://github.com/python/cpython/pull/25916
    https://github.com/python/cpython/pull/26503
    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/2024/11/msg00024.html
    https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html
    https://python-security.readthedocs.io/vuln/urllib-100-continue-loop.html
    https://security.netapp.com/advisory/ntap-20220407-0009/
    https://ubuntu.com/security/CVE-2021-3737
    https://www.oracle.com/security-alerts/cpujul2022.html

    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