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.

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.

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.