(1) Webmin 0.96 and (2) Usermin 0.90 with password timeouts enabled allow local and possibly remote attackers to bypass authentication and gain privileges via certain control characters in the authentication information, which can force Webmin or Usermin to accept arbitrary username/session ID combinations.

Cross-site scripting vulnerability in the authentication page for (1) Webmin 0.96 and (2) Usermin 0.90 allows remote attackers to insert script into an error page and possibly steal cookies.

Webmin before 0.5 does not restrict the number of invalid passwords that are entered for a valid username, which could allow remote attackers to gain privileges via brute force password cracking.

The web mail functionality in Usermin 1.x and Webmin 1.x allows remote attackers to execute arbitrary commands via shell metacharacters in an e-mail message.

Format string vulnerability in miniserv.pl Perl web server in Webmin before 1.250 and Usermin before 1.180, with syslog logging enabled, allows remote attackers to cause a denial of service (crash or memory consumption) and possibly execute arbitrary code via format string specifiers in the username parameter to the login form, which is ultimately used in a syslog call. NOTE: the code execution might be associated with an issue in Perl.

miniserv.pl in Webmin 1.962 on Windows mishandles special characters in query arguments to the CGI program.