Sebastian Krahmer of the SuSE security team discovered a remote command injection flaws in the gitweb, caused by an insufficient checking of the inputs used to build argument to perl's open() function. Remote attacker could use these flaws to run arbitrary commands with the privileges of the web server executing gitweb CGI scripts.
Issues are already fixed upstream in the latest git branches. It seems that the security consequences were not noticed when fixes were applied upstream, as multiple occurrences of the similar flaws were fixed in different upstream versions:
CVE-2008-5517 http://repo.or.cz/w/git.git?a=commitdiff;h=516381d5 (fixes issues in gitsnapshot and gitobject, first occurred in 1.5.6)
CVE-2008-5516 http://repo.or.cz/w/git.git?a=commitdiff;h=c582abae (fixes issue in gitsearch, first occurred in 1.5.5)
All current Fedora packages use version 1.5.6+, so neither of the issue apply to them. EPEL versions should be affected by one or both of the issues.