It was reported [1] that pyfribidi contains a buffer overflow in the log2visutf8() function due to the assumption that the string returned by fribidiunicodetoutf8() will be the same length as the original UTF-8 string. Due to changes in fribidi 0.19.1, for the Arabic language this is not the case as the joining added in fribidi causes some of the original 2-byte UTF-8 sequences to be come 3-bytes long.
The upstream report also includes a patch that is supposed to correct the issue by increasing the size of the buffer passed to fribidiunicodetoutf8().
Due to Fedora 11 and 12 containing fribidi 0.19.2, this would affect Fedora.
[1] http://sourceforge.net/tracker/?func=detail&aid=2676136&groupid=158366&atid=807545