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.

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.