c2faxrecv in capi4hylafax 01.02.03 allows remote attackers to execute arbitrary commands via null (\0) and shell metacharacters in the TSI string, as demonstrated by a fax from an anonymous number.
http://www.vupen.com/english/advisories/2006/3430
http://www.securityfocus.com/bid/19801
http://www.novell.com/linux/security/advisories/2007_4_sr.html
http://www.debian.org/security/2006/dsa-1165
http://security.gentoo.org/glsa/glsa-200610-05.xml
http://secunia.com/advisories/22450
http://secunia.com/advisories/21726