medium
6.5
CWE
400
Advisory Published
Updated

CVE-2021-3733

First published: Tue Aug 10 2021(Updated: )

Python is vulnerable to a denial of service, caused by a regular expression denial of service (ReDoS) flaw in the AbstractBasicAuthHandler class in urllib. By persuading a victim to visit a specially-crafted web site, a remote attacker could exploit this vulnerability to cause a denial of service condition.

Credit: secalert@redhat.com secalert@redhat.com

Affected SoftwareAffected VersionHow to fix
redhat/python3<0:3.6.8-39.el8_4
0:3.6.8-39.el8_4
redhat/rh-python38-babel<0:2.7.0-12.el7
0:2.7.0-12.el7
redhat/rh-python38-python<0:3.8.11-2.el7
0:3.8.11-2.el7
redhat/rh-python38-python-cryptography<0:2.8-5.el7
0:2.8-5.el7
redhat/rh-python38-python-jinja2<0:2.10.3-6.el7
0:2.10.3-6.el7
redhat/rh-python38-python-lxml<0:4.4.1-7.el7
0:4.4.1-7.el7
redhat/rh-python38-python-pip<0:19.3.1-2.el7
0:19.3.1-2.el7
redhat/rh-python38-python-urllib3<0:1.25.7-7.el7
0:1.25.7-7.el7
redhat/python27-python<0:2.7.18-4.el7
0:2.7.18-4.el7
IBM Cognos Analytics 11.2.x<=IBM Cognos Analytics 11.2.x
IBM Cognos Analytics 11.1.x<=IBM Cognos Analytics 11.1.x
redhat/python<3.6.14
3.6.14
redhat/python<3.7.11
3.7.11
redhat/python<3.8.10
3.8.10
redhat/python<3.9.5
3.9.5
debian/python2.7<=2.7.16-2+deb10u1<=2.7.18-8+deb11u1
2.7.16-2+deb10u4
debian/python3.7<=3.7.3-2+deb10u3
3.7.3-2+deb10u7
debian/python3.9<=3.9.2-1
ubuntu/python3.10<3.10.0~
3.10.0~
ubuntu/python3.4<3.4.3-1ubuntu1~14.04.7+
3.4.3-1ubuntu1~14.04.7+
ubuntu/python3.5<3.5.2-2ubuntu0~16.04.13+
3.5.2-2ubuntu0~16.04.13+
ubuntu/python3.6<3.6.9-1~18.04ubuntu1.6
3.6.9-1~18.04ubuntu1.6
ubuntu/python3.7<3.7.5-2ubuntu1~18.04.2
3.7.5-2ubuntu1~18.04.2
ubuntu/python3.8<3.8.0-3ubuntu1~18.04.2
3.8.0-3ubuntu1~18.04.2
ubuntu/python3.8<3.8.10-0ubuntu1~20.04
3.8.10-0ubuntu1~20.04
ubuntu/python3.9<3.9.5-3~20.04.1
3.9.5-3~20.04.1
ubuntu/python3.9<3.9.7-1
3.9.7-1
Python Python<3.6.14
Python Python>=3.7.0<3.7.11
Python Python>=3.8.0<3.8.10
Python Python>=3.9.0<3.9.5
Python Python=3.10.0
Redhat Codeready Linux Builder=8.0
Redhat Codeready Linux Builder For Ibm Z Systems=8.0
Redhat Codeready Linux Builder For Power Little Endian=8.0
Redhat Enterprise Linux=8.0
Redhat Enterprise Linux Eus=8.4
Redhat Enterprise Linux For Ibm Z Systems=8.0
Redhat Enterprise Linux For Ibm Z Systems Eus=8.4
Redhat Enterprise Linux For Power Little Endian=8.0
Redhat Enterprise Linux For Power Little Endian Eus=8.4
Redhat Enterprise Linux Server Aus=8.4
Redhat Enterprise Linux Server For Power Little Endian Update Services For Sap Solutions=8.4
Redhat Enterprise Linux Server Tus=8.4
Redhat Enterprise Linux Server Update Services For Sap Solutions=8.4
Fedoraproject Extra Packages For Enterprise Linux=7.0
Fedoraproject Fedora=33
Fedoraproject Fedora=34
Fedoraproject Fedora=35
Fedoraproject Fedora=36
Netapp Management Services For Element Software And Netapp Hci
NetApp ONTAP Select Deploy administration utility
Netapp Solidfire\, Enterprise Sds \& Hci Storage Node
Netapp Hci Compute Node Firmware

Remedy

https://bugs.python.org/issue43075

Remedy

https://github.com/python/cpython/commit/7215d1ae25525c92b026166f9d5cac85fb

Remedy

https://github.com/python/cpython/pull/24391

Remedy

https://ubuntu.com/security/CVE-2021-3733

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is CVE-2021-3733?

    CVE-2021-3733 is a vulnerability in urllib's AbstractBasicAuthHandler class that allows an attacker to trigger a Regular Expression Denial of Service (ReDOS) during an authentication request.

  • What can an attacker do with CVE-2021-3733?

    An attacker who controls a malicious HTTP server can exploit CVE-2021-3733 to launch a ReDOS attack on an HTTP client (e.g., web browser).

  • How severe is CVE-2021-3733?

    CVE-2021-3733 has a severity rating of 6.5, which is considered medium.

  • Which software versions are affected by CVE-2021-3733?

    CVE-2021-3733 affects Python versions 3.6.14, 3.7.11, 3.8.10, and 3.9.5, as well as other related packages.

  • How can I mitigate CVE-2021-3733?

    To mitigate CVE-2021-3733, it is recommended to update to the fixed versions of Python and related packages provided by Red Hat.

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