CVE-2006-2194

The winbind plugin in pppd for ppp 2.4.4 and earlier does not check the return code from the setuid function call, which might allow local users to gain privileges by causing setuid to fail, such as exceeding PAM limits for the maximum number of user processes, which prevents the winbind NTLM...

Symbolic link problem in pppd

It's possible to change file permisions via symbolic link by using it as a tty device...