CVE-2021-24025

CVE-2021-24025 is a critical vulnerability affecting Facebook HHVM versions prior to 4.56.3 and various other versions up to 4.98.0. It stems from incorrect string size calculations within the preg_quote function, leading to an integer overflow and subsequent heap overflow when processing large input strings. With a CVSS score of 9.8 (CRITICAL), this vulnerability is remotely exploitable with low attack complexity, allowing for potential complete compromise of confidentiality, integrity, and availability. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered significant community discussion, indicating awareness and potential for future exploitation.