Sylpheed-Claws before 2.2.2 and Sylpheed before 2.2.6 allow remote attackers to bypass the URI check functionality and makes it easier to conduct phishing attacks via a URI that begins with a space character.
Format string vulnerability in send_message.c for Sylpheed-claws 0.9.4 through 0.9.6 allows remote SMTP servers to cause a denial of service (crash) in sylpheed via format strings in an error message.