The resolve_redirects function in sessions.py in requests 2.1.0 through 2.5.3 allows remote attackers to conduct session fixation attacks via a cookie without a host value in a redirect.

References

• https://nvd.nist.gov/vuln/detail/CVE-2015-2296
• https://warehouse.python.org/project/requests/2.6.0/
• http://advisories.mageia.org/MGASA-2015-0120.html
• http://lists.fedoraproject.org/pipermail/package-announce/2015-March/153594.html
• http://www.mandriva.com/security/advisories?name=MDVSA-2015:133
• http://www.openwall.com/lists/oss-security/2015/03/14/4
• http://www.openwall.com/lists/oss-security/2015/03/15/1
• http://www.ubuntu.com/usn/USN-2531-1
• psf/requests@3bd8afb