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TUCoPS :: Windows Net Apps :: ciach084.txt

Windows NT NtOpenProcessToken vulnerability


[ For Public Release ]

                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                  Windows NT NtOpenProcessToken Vulnerability

July 22, 1997 18:00 GMT                                            Number H-84
PROBLEM:       A vulnerability exists in a Microsoft Windows NT operating
               system kernel routine.
PLATFORM:      Windows NT Workstation and Server 4.0.
DAMAGE:        Exploit allows local users to gain Administrator privileges.
SOLUTION:      Apply the Microsoft patch and follow the policy guidelines
               described below.
VULNERABILITY  Exploit is widely available, but attack is only successfully
ASSESSMENT:    executed locally.


A vulnerability in Microsoft Windows NT 4.0 allows a user to locally execute a
utility to gain administrator privileges.  The utility is successfully
executed from most local user accounts, regardless of the permissions.  An
exception to this is the Guest account.  Because the attacker must have a
valid account and physical access to the system for this attack to be
successful, the attacker is most likely to be an "insider".


The utility works by adding the user (or attacker) to the Administrators'
Group.  The Administrators group is usually designed such that its members can
modify the registry, including adding and deleting users, as well as perform
other security functions (changing passwords, permissions, etc.).  This group
and any other group or user who has the "Debug Programs" privilege (used for
testing and debugging programs) will always be able to successfully execute
this utility, as well as many other utilities with security risks.


In order to mitigate this and similar attacks, CIAC recommends that the
following four configuration controls be applied:

1.  Apply the Microsoft hotfix  located below.  CIAC highly recommends that
Service Pack 3 is installed first.

Microsoft's Debug Right Vulnerability hotfix location for the U.S. version of

2.  Limit debug rights to those trusted users who must conduct testing or
debugging functions on the system.  In general, very few users need the
ability to test and debug systems.  Privileges should be granted on an
individual case by case basis.  If possible, avoid granting entire groups this
privilege.  Once the Microsoft hotfix described in item 1 above is applied,
this specific attack will only work if executed from accounts which have
legitimately been granted the debug right, or are already a member of the
Administrators' Group.  To check or change who has the "Debug Programs" Right:

1. Log in as an administrator (or equivalent privileges)on either Windows NT
   Workstation or Server (process is similar for both).
2. Open "User Manager".
3. Choose "Policies", then "User Rights".
4. Check the "Show Advanced User Rights" box.  ("Debug Programs" is an
   Advanced User Right).
5. Choose the "Debug Programs" Right, and Add or Remove users/groups as

3.  Prohibit most users from having physical access to the  NT server
consoles.  This can be accomplished  by setting the "Log on Locally" right to
only a few trusted administrators.  In addition, servers should physically
reside in a location that is secured, and physical access is controlled, such
as a locked computer room or (well-ventilated) closet.

4.  As with any operating system, limit the number of users granted
administrator privileges, and limit the number of users who have access to the
Administrator account.  Make sure the activities of these accounts 
(especially  Registry changes) are audited to provide a traceable record of
events.  Users should only use their Administrator accounts when necessary. 
They should also have a working account not in the Administrators' group to
use when not conducting administrator responsibilities.  Permissions should be
minimally granted, so that users have just enough privileges to accomplish
their tasks, and are provided limited access, especially to system files.


CIAC would like to thank Karan Khanna and Microsoft for their contributions
in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 510-422-8193
    FAX:      +1 510-423-8002
    STU-III:  +1 510-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
   Anonymous FTP: (
   Modem access:        +1 (510) 423-4753 (28.8K baud)
                        +1 (510) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. CIAC-NOTES for Notes, a collection of computer security articles;
3. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
4. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called Majordomo, which ignores E-mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-mail message body, substituting
ciac-bulletin, ciac-notes, spi-announce OR spi-notes for list-name:

E-mail to or
        subscribe list-name
  e.g., subscribe ciac-notes

You will receive an acknowledgment email immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the email.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.

If you include the word 'help' in the body of an email to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via email, etc.

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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H-81: HP-UX swinstall command in SD-UX Vulnerability
H-82: Lynx Temporary Files & Downloading Vulnerabilities
H-83: Solaris ping Vulnerability
H-84: Windows NT NtOpenProcessToken Vulnerability

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