Wordpress 1.5 through 2.3.1 uses cookie values based on the MD5 hash of a password MD5 hash, which allows attackers to bypass authentication by obtaining the MD5 hash from the user database, then generating the authentication cookie from that hash.

References

• https://nvd.nist.gov/vuln/detail/CVE-2007-6013
• https://exchange.xforce.ibmcloud.com/vulnerabilities/38578
• https://www.redhat.com/archives/fedora-package-announce/2008-January/msg00079.html
• https://www.redhat.com/archives/fedora-package-announce/2008-January/msg00098.html
• http://lists.grok.org.uk/pipermail/full-disclosure/2007-November/058576.html
• http://osvdb.org/40801
• http://secunia.com/advisories/27714
• http://secunia.com/advisories/28310
• http://securityreason.com/securityalert/3375
• http://trac.wordpress.org/ticket/5367
• http://www.cl.cam.ac.uk/~sjm217/advisories/wordpress-cookie-auth.txt
• http://www.securityfocus.com/archive/1/483927/100/0/threaded
• http://www.securitytracker.com/id?1018980
• http://www.vupen.com/english/advisories/2007/3941