Webmin, Usermin: Remote code execution through PAM authentication

Background

Webmin and Usermin are web-based system administration consoles. Webmin allows an administrator to easily configure servers and other features. Usermin allows users to configure their own accounts, execute commands, and read e-mails.

Description

Keigo Yamazaki discovered that the miniserv.pl webserver, used in both Webmin and Usermin, does not properly validate authentication credentials before sending them to the PAM (Pluggable Authentication Modules) authentication process. The default configuration shipped with Gentoo does not enable the “full PAM conversations” option and is therefore unaffected by this flaw.

Impact

A remote attacker could bypass the authentication process and run any command as the root user on the target server.

Workaround

Do not enable “full PAM conversations” in the Authentication options of Webmin and Usermin.

Resolution

All Webmin users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-admin/webmin-1.230"

All Usermin users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-admin/usermin-1.160"