CVE-2018-20852

NameCVE-2018-20852
Descriptionhttp.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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-1889-1, DLA-1906-1
NVD severitymedium

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
python2.7 (PTS)jessie2.7.9-2+deb8u1vulnerable
jessie (security)2.7.9-2+deb8u5fixed
stretch (security), stretch2.7.13-2+deb9u3vulnerable
buster2.7.16-2+deb10u1fixed
bullseye, sid2.7.17-1fixed
python3.4 (PTS)jessie3.4.2-1vulnerable
jessie (security)3.4.2-1+deb8u7fixed
python3.5 (PTS)stretch (security), stretch3.5.3-1+deb9u1vulnerable
python3.7 (PTS)buster3.7.3-2fixed
bullseye, sid3.7.5-2fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
python2.7source(unstable)2.7.16-3
python2.7sourcebuster2.7.16-2+deb10u1
python2.7sourcejessie2.7.9-2+deb8u4DLA-1906-1
python3.4source(unstable)(unfixed)
python3.4sourcejessie3.4.2-1+deb8u6DLA-1889-1
python3.5source(unstable)(unfixed)
python3.7source(unstable)3.7.3~rc1-1

Notes

[stretch] - python2.7 <no-dsa> (Minor issue)
https://bugs.python.org/issue35121
https://python-security.readthedocs.io/vuln/cookie-domain-check.html
https://github.com/python/cpython/commit/979daae300916adb399ab5b51410b6ebd0888f13 (2.7.x branch)
https://github.com/python/cpython/commit/42ad4101d3ba7ca3c371dadf0f8880764c9f15fb (v3.4.10)
https://github.com/python/cpython/commit/4749f1b69000259e23b4cc6f63c542a9bdc62f1b (v3.5.7)
https://github.com/python/cpython/commit/b241af861b37e20ad30533bc0b7e2e5491cc470f (v3.6.9rc1)
https://github.com/python/cpython/commit/e5123d81ffb3be35a1b2767d6ced1a097aaf77be (v3.7.3rc1)

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