The key validation code in GnuPG before 1.2.2 does not properly determine the validity of keys with multiple user IDs and assigns the greatest validity of the most valid user ID, which prevents GnuPG from warning the encrypting user when a user ID does not have a trusted path.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A135
https://exchange.xforce.ibmcloud.com/vulnerabilities/11930
http://www.turbolinux.com/security/TLSA-2003-34.txt
http://www.securityfocus.com/bid/7497
http://www.redhat.com/support/errata/RHSA-2003-176.html
http://www.redhat.com/support/errata/RHSA-2003-175.html
http://www.mandriva.com/security/advisories?name=MDKSA-2003:061
http://www.linuxsecurity.com/advisories/gentoo_advisory-3266.html
http://www.linuxsecurity.com/advisories/engarde_advisory-3258.html
http://www.kb.cert.org/vuls/id/397604
http://marc.info/?l=bugtraq&m=105362224514081&w=2
http://marc.info/?l=bugtraq&m=105311804129104&w=2
http://marc.info/?l=bugtraq&m=105301357425157&w=2
http://marc.info/?l=bugtraq&m=105215110111174&w=2
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000694