CVE-2018-20852

python: Cookie domain check returns incorrect results

Published Jul 13, 2019 CVSS 3.1 · 4.3 Medium EPSS 3.7% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-1889-1 python3.4 security update
Debian DLA Debian DLA DLA-1906-1 python2.7 security update
Debian DLA Debian DLA DLA-2280-1 python3.5 security update
Debian DLA Debian DLA DLA-2337-1 python2.7 security update
EUVD EUVD EUVD-2018-13392 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.
Ubuntu USN Ubuntu USN USN-4127-1 Python vulnerabilities
Ubuntu USN Ubuntu USN USN-4127-2 Python vulnerabilities
Ubuntu USN Ubuntu USN USN-6891-1 Python vulnerabilities
History
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Oct 7, 2026, 6:24 PM
Reserved
Jul 13, 2019, 12:00 AM
Status
Modified
Published
Jul 13, 2019, 9:15 PM
Modified
Oct 7, 2026, 7:17 PM
Severity
Moderate
Public date
Oct 31, 2018, 12:00 AM