Published: 15 February 2011
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.
From the Ubuntu security team
Kees Cook discovered that some shadow utilities did not correctly validate user input. A local attacker could exploit this flaw to inject newlines into the /etc/passwd file. If the system was configured to use NIS, this could lead to existing NIS groups or users gaining or losing access to the system, resulting in a denial of service or unauthorized access.