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 advisories/code/issues, web search, more)
ReferencesDLA-1889-1, DLA-1906-1, DLA-2280-1, DLA-2337-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
python2.7 (PTS)buster2.7.16-2+deb10u1fixed
bullseye2.7.18-8fixed
python3.7 (PTS)buster3.7.3-2+deb10u3fixed
buster (security)3.7.3-2+deb10u4fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
python2.7sourcejessie2.7.9-2+deb8u4DLA-1906-1
python2.7sourcestretch2.7.13-2+deb9u4DLA-2337-1
python2.7sourcebuster2.7.16-2+deb10u1
python2.7source(unstable)2.7.16-3
python3.4sourcejessie3.4.2-1+deb8u6DLA-1889-1
python3.4source(unstable)(unfixed)
python3.5sourcestretch3.5.3-1+deb9u2DLA-2280-1
python3.5source(unstable)(unfixed)
python3.7source(unstable)3.7.3~rc1-1

Notes

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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