PHP 4.4.4, 5.1.6, and other versions, when running on Apache, allows local users to modify behavior of other sites hosted on the same web server by modifying the mbstring.func_overload setting within .htaccess, which causes this setting to be applied to other virtual hosts on the same server.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.003
EPSS Ranking 50.2%