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.
release.debian.org/proposed-updates/stable_diffs/squirrelmail_1.4.15-4+lenny2.debdiff
secunia.com/advisories/35140
www.debian.org/security/2009/dsa-1802
www.mandriva.com/security/advisories?name=MDVSA-2009:122
www.securityfocus.com/archive/1/503718/100/0/threaded
www.redhat.com/archives/fedora-package-announce/2009-May/msg01195.html
www.redhat.com/archives/fedora-package-announce/2009-May/msg01202.html