ext/imap/php_imap.c in PHP 5.x and 7.x before 7.3.0 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via an empty string in the message argument to the imap_mail function.
- https://hackerone.com/reports/456727
- https://github.com/syadg123/pigat
- https://github.com/teamssix/pigat