The is_a function in PHP 5.3.7 and 5.3.8 triggers a call to the __autoload function, which makes it easier for remote attackers to execute arbitrary code by providing a crafted URL and leveraging potentially unsafe behavior in certain PEAR packages and custom autoloaders.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.014
EPSS Ranking 79.3%