The build_index_from_tree function in index.py in Dulwich before 0.9.9 allows remote attackers to execute arbitrary code via a commit with a directory path starting with .git/, which is not properly handled when checking out a working tree.
http://www.openwall.com/lists/oss-security/2015/03/22/26
http://www.debian.org/security/2015/dsa-3206
http://lists.fedoraproject.org/pipermail/package-announce/2015-April/154551.html
http://lists.fedoraproject.org/pipermail/package-announce/2015-April/154523.html