The ACL plugin in Dovecot before 1.1.4 treats negative access rights as if they are positive access rights, which allows attackers to bypass intended access restrictions.
https://www.redhat.com/archives/fedora-package-announce/2008-October/msg00844.html
https://www.redhat.com/archives/fedora-package-announce/2008-October/msg00816.html
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10376
https://euvd.enisa.europa.eu/vulnerability/EUVD-2008-4557
http://www.vupen.com/english/advisories/2008/2745
http://www.securityfocus.com/bid/31587
http://www.redhat.com/support/errata/RHSA-2009-0205.html
http://www.mandriva.com/security/advisories?name=MDVSA-2008:232
http://www.dovecot.org/list/dovecot-news/2008-October/000085.html
http://secunia.com/advisories/36904
http://secunia.com/advisories/33624
http://secunia.com/advisories/33149
http://secunia.com/advisories/32471
http://secunia.com/advisories/32164
http://lists.opensuse.org/opensuse-security-announce/2009-02/msg00002.html