__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft LDAP Over SSL Password Vulnerability [Microsoft Security Bulletin MS01-036] June 26, 2001 01:00 GMT Number L-101 ______________________________________________________________________________ PROBLEM: An LDAP function fails to check the permissions of a requester when the directory principal=domain user and data attribute=domain password. If the LDAP server is configured to support LDAP over SSL sessions, any user who can establish a connection to the LDAP server can exploit this vulnerability. PLATFORM: Windows 2000. This only affects those servers configured with LDAP over SSL, not default configurations. DAMAGE: This is an elevation of privileges vulnerability. Potentially, the worst case scenario is an attacker establishes a connection, changes the Administrator password, and accesses the Administrator account. Then he has control of the system. SOLUTION: Apply the patch prescribed by Microsoft. ______________________________________________________________________________ VULNERABILITY MEDIUM to HIGH, depending on system and network configuration. ASSESSMENT: Mitigating factors include blocking port 636 at a firewall. ______________________________________________________________________________ [****** Start Microsoft Advisory ******] - ---------------------------------------------------------------------- Title: Function Exposed via LDAP over SSL Could Enable Passwords to be Changed Date: 25 June 2001 Software: Windows 2000 Impact: Privilege Elevation Bulletin: MS01-036 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-036.asp. - ---------------------------------------------------------------------- Issue: ====== This vulnerability involves an LDAP function that is only available if the LDAP server has been configured to support LDAP over SSL sessions, and whose purpose is to allow users to change the data attributes of directory principals. By design, the function should check the authorizations of the user before completing the request; however, it contains an error that manifests itself only when the directory principal is a domain user and the data attribute is the domain password -- when this is the case, the function fails to check the permissions of the requester, with the result that it could be possible for a user to change any other user's domain login password. An attacker could change another user's password for either of two purposes: to cause a denial of service by preventing the other user from logging on, or in order to log into the user's account and gain any privileges the user had. Clearly, the most serious case would be one in which the attacker changed a domain administrator's password and logged into the administrator's account. By design, the function affected can be called by any user who can connect to the LDAP server, including users who connect via anonymous sessions. As a result, any user who could establish a connection with an affected server could exploit the vulnerability. Mitigating Factors: ==================== - LDAP over SSL sessions cannot be conducted unless the administrator has installed a digital certificate on the LDAP server. As a result, default installations of Windows 2000 are not affected by this vulnerability. - If the firewall is configured to block tcp port 636, the vulnerability could not be exploited by outside users. - This vulnerability could not be used to change the password of local user accounts on individual machines. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-036.asp for information on obtaining this patch. Acknowledgment: =============== - Jon McDonald (http://www.entrigue.net) - Russ Cooper (http://www.ntbugtraq.com) - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. [****** End Microsoft Advisory ******] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Center, 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. 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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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