Webmin, Usermin: Format string vulnerability

Background

Webmin is a web-based interface for Unix-like systems. Usermin is a simplified version of Webmin designed for use by normal users rather than system administrators.

Description

Jack Louis discovered that the Webmin and Usermin “miniserv.pl” web server component is vulnerable to a Perl format string vulnerability. Login with the supplied username is logged via the Perl “syslog” facility in an unsafe manner.

Impact

A remote attacker can trigger this vulnerability via a specially crafted username containing format string data. This can be exploited to consume a large amount of CPU and memory resources on a vulnerable system, and possibly to execute arbitrary code of the attacker’s choice with the permissions of the user running Webmin.

Workaround

There is no known workaround at this time.

Resolution

All Webmin users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-admin/webmin-1.250"

All Usermin users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-admin/usermin-1.180"