gpg (aka GnuPG) 1.0.4 and other versions imports both public and private keys from public key servers without notifying the user about the private keys, which could allow an attacker to break the web of trust.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5803
http://www.securityfocus.com/bid/2153
http://www.securityfocus.com/archive/1/152197
http://www.redhat.com/support/errata/RHSA-2000-131.html
http://www.linux-mandrake.com/en/updates/2000/MDKSA-2000-087.php3
http://www.debian.org/security/2000/20001225b
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000368