CVE-2023-29383

In Shadow 4.13, it is possible to inject control characters into fields
provided to the SUID program chfn (change finger). Although it is not
possible to exploit this directly (e.g., adding a new user fails because \n
is in the block list), it is possible to misrepresent the /etc/passwd file
when viewed. Use of \r manipulations and Unicode characters to work around
blocking of the : character make it possible to give the impression that a
new user has been added. In other words, an adversary may be able to
convince a system administrator to take the system offline (an indirect,
social-engineered denial of service) by demonstrating that “cat
/etc/passwd” shows a rogue user account.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1034482&gt;