Sylpheed is a lightweight email client and newsreader. Sylpheed-claws is a 'bleeding edge' version of Sylpheed.
Sylpheed and Sylpheed-claws fail to properly handle non-ASCII characters in email headers when composing reply messages.
An attacker can send an email containing a malicious non-ASCII header which, when replied to, would cause the program to crash, potentially allowing the execution of arbitrary code with the privileges of the user running the software.
There is no known workaround at this time.
All Sylpheed users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=mail-client/sylpheed-1.0.3"
All Sylpheed-claws users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=mail-client/sylpheed-claws-1.0.3"