J-Security Center

Title: Webmin / Usermin Remote PAM Authentication Bypass Vulnerability

Severity: CRITICAL

Description:

Usermin is a Web-based user interface for Unix and Linux users. It is designed to allow users to access email and configure various user settings. Webmin is a Web-based interface for system administration of Unix and Linux operating systems.

Webmin and Usermin are susceptible to a remote authentication bypass vulnerability. This issue presents itself when the 'Support full PAM conversations?' option is enabled. It should be noted that this is not enabled by default.

This issue is present in the 'miniserv.pl' Web server that is bundled with these applications. Due to insufficient input validation, shell metacharacters may be employed to bypass the authentication mechanism to execute arbitrary commands with superuser privileges.

Specifically, 'miniserv.pl' utilizes pipes to communicate with a child process in order to check supplied credentials with PAM. The child process is used to call the PAM modules, and if certain metacharacters are passed to the child, attackers can bypass the authentication process.

Due to the nature of these applications, full system compromise is very likely after gaining access.

Affected Products:

  • Gentoo Linux
  • MandrakeSoft Corporate Server 2.1.0
  • MandrakeSoft Corporate Server 2.1.0 x86_64
  • MandrakeSoft Corporate Server 3.0.0
  • MandrakeSoft Corporate Server 3.0.0 x86_64
  • MandrakeSoft Linux Mandrake 10.1.0
  • MandrakeSoft Linux Mandrake 10.1.0 x86_64
  • MandrakeSoft Linux Mandrake 10.2.0
  • MandrakeSoft Linux Mandrake 10.2.0 x86_64
  • MandrakeSoft Linux Mandrake 2006.0.0
  • MandrakeSoft Linux Mandrake 2006.0.0 x86_64
  • S.u.S.E. Linux Personal 9.0.0
  • S.u.S.E. Linux Personal 9.0.0 x86_64
  • S.u.S.E. Linux Personal 9.1.0
  • S.u.S.E. Linux Personal 9.1.0 x86_64
  • S.u.S.E. Linux Professional 9.0.0
  • S.u.S.E. Linux Professional 9.0.0 x86_64
  • S.u.S.E. Linux Professional 9.1.0
  • S.u.S.E. Linux Professional 9.1.0 x86_64
  • Webmin Usermin 1.130.0
  • Webmin Usermin 1.140.0
  • Webmin Usermin 1.150.0
  • Webmin Webmin 1.200.0
  • Webmin Webmin 1.210.0
  • Webmin Webmin 1.220.0

References:

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