Unknown vulnerability in Apache 2.0.51 prevents "the merging of the Satisfy directive," which could allow attackers to obtain access to restricted resources contrary to the specified authentication configuration.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17473
http://www.trustix.org/errata/2004/0049
http://www.securityfocus.com/bid/11239
http://www.apacheweek.com/features/security-20
http://www.apache.org/dist/httpd/patches/apply_to_2.0.51/CAN-2004-0811.patch