Microsoft Security Bulletin MS99-041
Tool Available for "RASMAN Security Descriptor" Vulnerability
Patch Availability Information Updated: March 21, 2003
Originally Posted: September 30, 1999
Microsoft has released a patch that eliminates a vulnerability in Microsoft® Windows NT® 4.0. The vulnerability could enable a user to execute arbitrary code on a Windows NT machine under certain conditions.
Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/technet/security/bulletin/fq99-041.mspx.
The security descriptor that secures the Remote Access Connection Manager, RASMAN.EXE, contains an inappropriate ACE in its DACL and would allow an unprivileged user to levy requests on it via the Service Control Manager. Among the actions that could be requested is to change the location and name of the executable code for the service. By doing so, a malicious user could substitute arbitrary code for the legitimate service, which then would run in a System Context.
A malicious user could only exploit this vulnerability if he or she had a valid userid and password on the target machine. If the machine allowed users to log on from the network, the vulnerability could be remotely exploited. In addition, the arbitrary code could, under certain conditions, reside on a remote machine. A tool is available to reset the permissions to the appropriate value and eliminate the vulnerability, and should be run against any machine that allows unprivileged users to perform either interactive or network logons under any account.
Affected Software Versions
- Microsoft Windows NT 4.0 Workstation
- Microsoft Windows NT 4.0 Server
- Microsoft Windows NT 4.0 Server, Enterprise Edition
- Microsoft Windows NT 4.0 Server, Terminal Server Edition
Vulnerability Identifier: CVE-1999-0886
Note The URL above lists the tool as residing in the "Hotfixes-PostSP6" folder even though Service Pack 6 has not shipped as of this writing. This was done because the vulnerability was discovered too late to be corrected in SP6, and the tool therefore needs to be run even on SP6 systems. The FAQ contains more information on this subject.
Please see the following references for more information related to this issue.
- Microsoft Security Bulletin MS99-041: Frequently Asked Questions, http://www.microsoft.com/technet/security/bulletin/fq99-041.mspx.
- Microsoft Knowledge Base (KB) article 242294, Security Descriptor Allows Privilege Elevation on Remote Computers, http://support.microsoft.com/default.aspx?scid=kb;en-us;242294&sd=tech.
Note It may take 24 hours from the original posting of this bulletin for this KB article to be visible.
- Microsoft Security web site, http://www.microsoft.com/technet/security/default.mspx.
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft Technical Support is available at http://support.microsoft.com/contactussupport/?ws=support.
Microsoft acknowledges Alberto Rodríguez Aragonés for bringing this issue to our attention.
- September 30, 1999: Bulletin Created.
- V2.0 (March 21, 2003): Introduced versioning and updated patch availability information.
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