gitweb/gitweb.perl in gitweb in Git 1.6.x before 1.6.0.6, 1.5.6.x before 1.5.6.6, 1.5.5.x before 1.5.5.6, 1.5.4.x before 1.5.4.7, and other versions after 1.4.3 allows local repository owners to execute arbitrary commands by modifying the diff.external configuration variable and executing a crafted gitweb query.
https://www.redhat.com/archives/fedora-package-announce/2008-December/msg01170.html
https://www.redhat.com/archives/fedora-package-announce/2008-December/msg01169.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/47528
http://www.ubuntu.com/usn/USN-723-1
http://www.openwall.com/lists/oss-security/2009/01/20/2
http://www.openwall.com/lists/oss-security/2009/01/15/2
http://www.gentoo.org/security/en/glsa/glsa-200903-15.xml
http://securityreason.com/securityalert/4922
http://secunia.com/advisories/34194
http://secunia.com/advisories/33964
http://secunia.com/advisories/33282