Buffer overflow in Sylpheed before 1.0.3 and other versions before 1.9.5 allows remote attackers to execute arbitrary code via an e-mail message with certain headers containing non-ASCII characters that are not properly handled when the user replies to the message.
http://www.redhat.com/support/errata/RHSA-2005-303.html
http://www.gentoo.org/security/en/glsa/glsa-200503-26.xml
http://sylpheed.good-day.net/changelog.html.en
http://sylpheed.good-day.net/changelog-devel.html.en