CVE 2009-0034
parse.c in sudo 1.6.9p17 through 1.6.9p19 does not properly interpret a system group (aka %group) in the sudoers file during authorization decisions for a user who belongs to that group, which allows local users to leverage an applicable sudoers file and gain root privileges via a sudo command.
See the 
CVE page on Mitre.org
for more details.
