The mod_auth_shadow module 1.0 through 1.5 and 2.0 for Apache with AuthShadow enabled uses shadow authentication for all locations that use the require group directive, even when other authentication mechanisms are specified, which might allow remote authenticated users to bypass security restrictions.
https://exchange.xforce.ibmcloud.com/vulnerabilities/22520
http://www.securityfocus.com/bid/15224
http://www.debian.org/security/2005/dsa-844
http://secunia.com/advisories/17348
http://secunia.com/advisories/17067
http://secunia.com/advisories/17060/
http://frontal1.mandriva.com/security/advisories?name=MDKSA-2005:200