Fossil is a simple, high-reliability, distributed software configuration management system.
Fossil does not properly validate SSH sync protocol URLs.
A remote attacker, by enticing a user to open a specially crafted URL, could possibly execute arbitrary commands with the privileges of the user running the application.
There is no known workaround at this time.
All Fossil users should upgrade to the latest version:
# emerge --sync # emerge --ask --oneshot --verbose ">=dev-vcs/fossil-2.4"