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CVE Vulnerabilities

CVE-2021-3733

Uncontrolled Resource Consumption

Published: Mar 10, 2022 | Modified: Nov 03, 2025
CVSS 3.x
6.5
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.x
4 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P
RedHat/V2
RedHat/V3
6.5 MODERATE
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Ubuntu
MEDIUM
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Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2021-3733
CWEhttps://cwe.mitre.org/data/definitions/400.html

Theres a flaw in urllibs 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.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

NameVendorStart VersionEnd Version
PythonPython*3.6.14 (excluding)
PythonPython3.7.0 (including)3.7.11 (excluding)
PythonPython3.8.0 (including)3.8.10 (excluding)
PythonPython3.9.0 (including)3.9.5 (excluding)
PythonPython3.10.0 (including)3.10.0 (including)
Red Hat Enterprise Linux 8RedHatpython3-0:3.6.8-39.el8_4*
Red Hat Enterprise Linux 8RedHatpython39:3.9-8050020210811100211.d428a79b*
Red Hat Enterprise Linux 8RedHatpython39-devel:3.9-8050020210811100211.d428a79b*
Red Hat Enterprise Linux 8RedHatpython38:3.8-8060020220120164031.5294be16*
Red Hat Enterprise Linux 8RedHatpython38-devel:3.8-8060020220120164031.5294be16*
Red Hat Enterprise Linux 8RedHatpython27:2.7-8060020220210185952.8cdc2268*
Red Hat Enterprise Linux 8RedHatpython3-0:3.6.8-39.el8_4*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-babel-0:2.7.0-12.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-0:3.8.11-2.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-cryptography-0:2.8-5.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-jinja2-0:2.10.3-6.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-lxml-0:4.4.1-7.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-pip-0:19.3.1-2.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatrh-python38-python-urllib3-0:1.25.7-7.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7RedHatpython27-python-0:2.7.18-4.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-babel-0:2.7.0-12.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-0:3.8.11-2.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-cryptography-0:2.8-5.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-jinja2-0:2.10.3-6.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-lxml-0:4.4.1-7.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-pip-0:19.3.1-2.el7*
Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSRedHatrh-python38-python-urllib3-0:1.25.7-7.el7*
Python3.10Ubuntuhirsute*
Python3.10Ubuntutrusty*
Python3.10Ubuntuxenial*
Python3.4Ubuntuesm-infra-legacy/trusty*
Python3.4Ubuntutrusty*
Python3.4Ubuntutrusty/esm*
Python3.5Ubuntuesm-infra-legacy/trusty*
Python3.5Ubuntuesm-infra/xenial*
Python3.5Ubuntutrusty*
Python3.5Ubuntutrusty/esm*
Python3.5Ubuntuxenial*
Python3.6Ubuntubionic*
Python3.6Ubuntuesm-infra/bionic*
Python3.6Ubuntutrusty*
Python3.6Ubuntuxenial*
Python3.7Ubuntubionic*
Python3.7Ubuntuesm-apps/bionic*
Python3.7Ubuntutrusty*
Python3.7Ubuntuxenial*
Python3.8Ubuntubionic*
Python3.8Ubuntuesm-apps/bionic*
Python3.8Ubuntuesm-infra/focal*
Python3.8Ubuntufocal*
Python3.8Ubuntutrusty*
Python3.8Ubuntuxenial*
Python3.9Ubuntuesm-apps/focal*
Python3.9Ubuntufocal*
Python3.9Ubuntutrusty*
Python3.9Ubuntuupstream*
Python3.9Ubuntuxenial*

Potential Mitigations

  • Mitigation of resource exhaustion attacks requires that the target system either:

  • The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

  • The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

References

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