The map_yp_alias function in functions/imap_general.php in SquirrelMail before 1.4.18 and NaSMail before 1.7 allows remote attackers to execute arbitrary commands via shell metacharacters in a username string that is used by the ypmatch program.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.048
EPSS Ranking 88.8%