The MITRE CVE dictionary describes this issue as:
plugins/acl/acl-backend-vfile.c in Dovecot 1.2.x before 1.2.15 and 2.0.x before 2.0.5 interprets an ACL entry as a directive to add to the permissions granted by another ACL entry, instead of a directive to replace the permissions granted by another ACL entry, in certain circumstances involving more specific entries that occur after less specific entries, which allows remote authenticated users to bypass intended access restrictions via a request to read or modify a mailbox.
Find out more about CVE-2010-3707 from the
MITRE CVE dictionary dictionary and
This issue did not affect the version of dovecot package, as shipped with Red
Hat Enterprise Linux 4 and 5. This issue affects the version of dovecot
package as shipped with Red Hat Enterprise Linux 6. The Red Hat Security
Response Team has rated this issue as having low security impact, a future
update may address this flaw.