Evolution is the mail client of the GNOME desktop environment. Camel is the Evolution Data Server module that handles mail functions.
The imap_rescan() function of the file camel-imap-folder.c does not properly sanitize the "SEQUENCE" response sent by an IMAP server before being used to index arrays.
A malicious or compromised IMAP server could trigger the vulnerability and execute arbitrary code with the permissions of the user running Evolution.
There is no known workaround at this time.
All Evolution users should upgrade evolution-data-server to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose "gnome-extra/evolution-data-server"