Disclosure summary
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.
Source-reported weakness categories
CWE-20
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
NIST National Vulnerability Database · NVD-CVE-2018-20852
Open original source · Updated Oct 07, 2026
Only CPE matches marked vulnerable=true are indexed. AND/OR platform conditions must be checked in the original NVD record.
| Vendor | Product / association | Version / bounds |
|---|---|---|
| python | python | * {"versionStartIncluding":"3.7.0","versionEndExcluding":"3.7.3"} |
Original records & references
- NIST NVD record
- CVE Program record
- access.redhat.com
- access.redhat.com
- bugs.python.org — Exploit, Issue Tracking, Vendor Advisory
- lists.debian.org
- lists.debian.org
- lists.debian.org
- lists.debian.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- python-security.readthedocs.io — Vendor Advisory
- security.gentoo.org
- usn.ubuntu.com
- usn.ubuntu.com
- www.oracle.com
- access.redhat.com
- access.redhat.com
- bugs.python.org — Exploit, Issue Tracking, Vendor Advisory
- lists.debian.org
- lists.debian.org
- lists.debian.org
- lists.debian.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- lists.fedoraproject.org
- python-security.readthedocs.io — Vendor Advisory
- security.gentoo.org
- usn.ubuntu.com
- usn.ubuntu.com
- www.oracle.com
PUBLISHED 2019-07-13T17:15:10-04:00
MODIFIED 2026-10-07T15:17:11-04:00
INGESTED 2026-10-08T12:30:34-04:00