Alert: Microsoft Security Bulletin - MS03-018

From: Russ (Russ.Cooper_at_RC.ON.CA)
Date: 05/28/03

  • Next message: Russ: "Alert: Microsoft Security Bulletin - MS03-019"
    Date:         Wed, 28 May 2003 13:30:12 -0400
    To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM
    
    

    http://www.microsoft.com/technet/security/bulletin/MS03-018.asp

    Cumulative Patch for Internet Information Service (811114)

    Originally posted: May 28, 2003

    Summary

    Who should read this bulletin: Customers hosting web servers using Microsoft® Windows NT® 4.0, Windows® 2000, or Windows® XP.

    Impact of vulnerability: Allow an attacker to execute code of their choice

    Maximum Severity Rating: Important

    Recommendation: Customers hosting web servers using Microsoft® Windows NT® 4.0, Windows® 2000, or Windows® XP should install the patch at the earliest opportunity.

    Affected Software:
    - Microsoft Internet Information Server 4.0
    - Microsoft Internet Information Services 5.0
    - Microsoft Internet Information Services 5.1

    Non Affected Software:
    - Microsoft Internet Information Services 6.0

    End User Bulletin: An end user version of this bulletin is available at: http://www.microsoft.com/security/security_bulletins/ms03-018.asp.

    Technical description:

    This patch is a cumulative patch that includes the functionality of all security patches released for IIS 4.0 since Windows NT 4.0 Service Pack 6a, and all security patches released to date for IIS 5.0 since Windows 2000 Service Pack 2 and IIS 5.1. A complete listing of the patches superseded by this patch is provided below, in the section titled "Additional information about this patch".

    In addition to all previously released security patches, this patch also includes fixes for the following newly discovered security vulnerabilities affecting IIS 4.0, 5.0 and 5.1:
    - A Cross-Site Scripting (CSS) vulnerability affecting IIS 4.0, 5.0 and 5.1 involving the error message that's returned to advise that a requested URL has been redirected. An attacker who was able to lure a user into clicking a link on his or her web site could relay a request containing script to a third-party web site running IIS, thereby causing the third-party site's response (still including the script) to be sent to the user. The script would then render using the security settings of the third-party site rather than the attacker's.
    - A buffer overrun that results because IIS 5.0 does not correctly validate requests for certain types of web pages known as server side includes. An attacker would need the ability to upload a Server-side include page to a vulnerable IIS server. If the attacker then requested this page, a buffer overrun could result, which would allow the attacker to execute code of their choice on the server with user-level permissions.
    - A denial of service vulnerability that results because of a flaw in the way IIS 4.0 and 5.0 allocate memory requests when constructing headers to be returned to a web client. An attacker would need the ability to upload an ASP page to a vulnerable IIS server. This ASP page, when called by the attacker, would attempt to return an extremely large header to the calling web client. Because IIS does not limit the amount of memory that can be used in this case, this could case IIS to fail as a result of running out of local memory.
    - A denial of service vulnerability that results because IIS 5.0 and 5.1 do not correctly handle an error condition when an overly long WebDAV request is passed to them. As a result an attacker could cause IIS to fail - however both IIS 5.0 and 5.1 will by default restart immediately after this failure.

    There is a dependency associated with this patch - it requires the patch from Microsoft Security Bulletin MS02-050 to be installed. If this patch is installed and MS02-050 is not present, client side certificates will be rejected. This functionality can be restored by installing the MS02-050 patch.

    Mitigating factors:

    Redirection Cross Site Scripting:
    - IIS 6.0 is not affected.
    - The vulnerability could only be exploited if the attacker could entice another user into visiting a web page and clicking a link on it, or opening an HTML mail.
    - The target page must be an ASP page, which uses Response.Redirect to redirect the client, to a new URL that is based on the incoming URL of current request.

    Server Side Include Web Pages Buffer Overrun
    - IIS 4.0, IIS 5.1 and IIS 6.0 are not affected.
    - The IIS Lockdown tool by default disables the ssinc.dll mapping, which will block this attack.
    - By default IIS 5.0 runs under a user account and not the system account. Therefore an attacker who successfully exploited the vulnerability would only gain user level permissions rather than administrative level permissions.
    - An attacker must have the ability to upload files to the IIS Server.

    ASP Headers Denial of Service
    - An attacker must have the ability to upload files to the IIS server.
    - IIS 5.0 will automatically restart after failing.
    - IIS 5.1 and IIS 6.0 are not affected.

    WebDAV Denial of Service
    - IIS 6.0 is not affected.
    - IIS 5.0 and 5.1 will restart automatically after this failure.
    - The IIS Lockdown tool disables WebDAV by default, which will block this attack.

    Vulnerability identifiers:

    Redirection Cross Site Scripting CAN-2003-0223

    Server Side Include Web Pages Buffer Overrun CAN-2003-0224

    ASP Headers Denial of Service CAN-2003-0225

    WebDAV Denial of Service CAN-2003-0226

    This email is sent to NTBugtraq automatically as a service to my subscribers. (v1.18)

    Cheers,
    Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor

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