Multiple CRLF injection vulnerabilities in (1) chfn and (2) chsh in shadow 1:4.1.4 allow local users to add new users or groups to /etc/passwd via the GECOS field.
http://secunia.com/advisories/42505
http://secunia.com/advisories/43345
https://exchange.xforce.ibmcloud.com/vulnerabilities/65564
http://www.debian.org/security/2011/dsa-2164
http://www.ubuntu.com/usn/USN-1065-1
http://www.vupen.com/english/advisories/2011/0396