The map_yp_alias function in functions/imap_general.php in SquirrelMail before 1.4.19-1 on Debian GNU/Linux, and possibly other operating systems and versions, allows remote attackers to execute arbitrary commands via shell metacharacters in a username string that is used by the ypmatch program. NOTE: this issue exists because of an incomplete fix for CVE-2009-1579.

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.