CVE 2005-2317
Shorewall 2.4.x before 2.4.1, 2.2.x before 2.2.5, and 2.0.x before 2.0.17, when MACLIST_TTL is greater than 0 or MACLIST_DISPOSITION is set to ACCEPT, allows remote attackers with an accepted MAC address to bypass other firewall rules or policies.
See the
CVE page on Mitre.org
for more details.