J-Security Center

Title: Multiple Linux Vendor userhelper/PAM Path Vulnerability

Severity: MODERATE

Description:

Because of double path vulnerabilities in the binary userhelper and PAM, it is possible to get root locally on RedHat 6.0 and 6.1 systems. Both userhelper and PAM follow ".." paths and userhelper allows you to specifiy a program to execute as an argument to the -w parameter (which is expected to have an entry in /etc/security/console.apps). Because of this, it's possible to specifiy a program such as "../../../tmp/myprog", which would (to userhelper) be "/etc/security/console.apps/../../../tmp/myprog". If "myprog" exists, PAM will then try to execute it (with the same filename). PAM first does a check to see if the configuration file for "../../../tmp/myprog" is in /etc/pam.d/ but also follows ".." directories -- to an attacker's custom pam configuration file. Specified inside the malicious configuration file (/tmp/myprog) would be arbitrary shared libraries to be opened with setuid privileges. The arbitrary libraries can be created by an attacker specifically to compromise superuser access, activating upon dlopen() by PAM.

This vulnerability also affects Mandrake Linux versions 6.0 and 6.1, as well as versions of TurboLinux Linux, version 6.0.2 and prior.

Affected Products:

  • MandrakeSoft Linux Mandrake 6.0.0
  • MandrakeSoft Linux Mandrake 6.1.0
  • RedHat Linux 6.0.0
  • RedHat Linux 6.1.0 i386
  • Turbolinux Turbolinux 3.5.0b2
  • Turbolinux Turbolinux 4.2.0
  • Turbolinux Turbolinux 4.4.0
  • Turbolinux Turbolinux 6.0.2

References:

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