August 25, 2004
The libDtHelp library is a core component of the Common Desktop Environment (CDE). It provides the help subsystem used by most CDE applications.
Exploitation of a buffer overflow in the libDtHelp library included with CDE can allow local attackers to gain root privileges.
The vulnerability specifically exists due to a lack of bounds checking on the LOGNAME environment variable. Local attackers can specify a long LOGNAME to trigger a buffer overflow in any application linked with libDtHelp. The overflow is activated once the help subsystem is accessed by selecting any option under the Help menu.
This vulnerability occurs in the same sequence of code as the previously disclosed DTSEARCHPATH and DTUSERSEARCHPATH vulnerabilities, described in CAN-2003-0834. However, the LOGNAME environment variable was not reported as a method of attack in related advisories.
US-CERT Vulnerability Note VU#575804, detailing the original attack vectors is available at:
Successful exploitation leads to root level access. CDE is a widely deployed default desktop environment for UNIX operating systems. Depending on the function of the machine, this vulnerability could lead to exposure of highly sensitive data. The vulnerability is easily exploitable even when stack protections are enabled, furthering the impact of exposure.
iDEFENSE has confirmed the existence of this vulnerability in Solaris 8 and Solaris 9 without the patches provided for in Sun Alert 57414. Hewlett Packard HP-UX, Silicon Graphics, Inc. Irix and SCO Unixware are also reportedly vulnerable.
If possible, remove the setuid bit from all applications linked to libDtHelp. The command 'ldd' will display libraries linked with the specified executable.
VI. VENDOR RESPONSE
Sun successfully addressed this issue with the patches described in Sun Alert 57414. Specific vendor advisories addressing CAN-2003-0834 are available in US-CERT Vulnerability Note VU#575804 (http://www.kb.cert.org/vuls/id/575804). It is believed that other vendor patches for CAN-2003-0834 will protect against this new attack vector.
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2003-0834 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.
VIII. DISCLOSURE TIMELINE
03/04/2004 Initial vendor contact
03/04/2004 iDEFENSE clients notified
03/31/2004 Initial vendor response
(Opengroup.org - further coordination requested)
04/19/2004 Initial vendor contact
(Hewlett-Packard, IBM, and Sun Microsystems)
04/19/2004 Initial vendor response (Sun Microsystems)
04/20/2004 Initial vendor response (Hewlett-Packard)
08/25/2004 Public disclosure
iDEFENSE Labs is credited with discovering this vulnerability.
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X. LEGAL NOTICES
Copyright (c) 2004 iDEFENSE, Inc.
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