medium
5.3
CWE
20
Advisory Published
CVE Published
Updated

CVE-2018-20852: Input Validation

First published: Wed Oct 31 2018(Updated: )

http.cookiejar.DefaultPolicy.domain_return_ok in Lib/http/cookiejar.py in Python before 3.7.3 does not correctly validate the domain: it can be tricked into sending existing cookies to the wrong server. An attacker may abuse this flaw by using a server with a hostname that has another valid hostname as a suffix (e.g., pythonicexample.com to steal cookies for example.com). When a program uses http.cookiejar.DefaultPolicy and tries to do an HTTP connection to an attacker-controlled server, existing cookies can be leaked to the attacker. This affects 2.x through 2.7.16, 3.x before 3.4.10, 3.5.x before 3.5.7, 3.6.x before 3.6.9, and 3.7.x before 3.7.3.

Credit: cve@mitre.org cve@mitre.org

Affected SoftwareAffected VersionHow to fix
redhat/python<0:2.7.5-88.el7
0:2.7.5-88.el7
redhat/python3<0:3.6.8-13.el7
0:3.6.8-13.el7
redhat/python3<0:3.6.8-23.el8
0:3.6.8-23.el8
redhat/rh-python36-python<0:3.6.9-2.el6
0:3.6.9-2.el6
redhat/python27-python<0:2.7.17-2.el6
0:2.7.17-2.el6
redhat/rh-python36-python<0:3.6.9-2.el7
0:3.6.9-2.el7
redhat/python27-python<0:2.7.17-2.el7
0:2.7.17-2.el7
Python Python>=2.0<=2.7.16
Python Python>=3.0.0<3.4.10
Python Python>=3.5.0<3.5.7
Python Python>=3.6.0<3.6.9
Python Python>=3.7.0<3.7.3
redhat/Python<3.4.10
3.4.10
redhat/Python<3.5.7
3.5.7
redhat/Python<3.6.9
3.6.9
redhat/Python<3.7.3
3.7.3
debian/python2.7
2.7.18-8+deb11u1
IBM Data Risk Manager<=2.0.6

Remedy

A potentially simple workaround in the absence of patch on affected versions is to set DomainStrict in the cookiepolicy that would make sure a literal match against domain. The disadvantage would be that cookie set on example.com would not be shared with subdomain which might break workflow.

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Reference Links

Parent vulnerabilities

(Appears in the following advisories)

Frequently Asked Questions

  • What is CVE-2018-20852?

    CVE-2018-20852 is a vulnerability in Python before version 3.7.3 that allows an attacker to trick the cookiejar into sending existing cookies to the wrong server.

  • How severe is CVE-2018-20852?

    CVE-2018-20852 has a severity rating of 5.3 (Medium).

  • Which versions of Python are affected by CVE-2018-20852?

    Python versions before 3.7.3 are affected by CVE-2018-20852.

  • How can I fix CVE-2018-20852?

    To fix CVE-2018-20852, upgrade your Python version to 3.7.3 or later.

  • Where can I find more information about CVE-2018-20852?

    You can find more information about CVE-2018-20852 at the following references: [1] [2] [3].

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