Published:
01 March 2001
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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.093 -- Microsoft Security Bulletin MS01-014 Malformed URL can cause Service Failure in IIS 5.0 and Exchange 2000 2 March 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Internet Information Server 5.0 Exchange 2000 Vendor: Microsoft Impact: Denial of Service Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- - - ---------------------------------------------------------------------- Title: Malformed URL can cause Service Failure in IIS 5.0 and Exchange 2000 Date: 01 March 2001 Software: IIS 5.0 and Exchange 2000 Impact: Denial of Service Bulletin: MS01-014 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-014.asp. - - ---------------------------------------------------------------------- Issue: ====== IIS 5.0 contains a flaw affecting the way that an URL is handled if it has a specific construction and its length is within a very narrow range of values. If such an URL were repeatedly sent to an affected system, a confluence of events could cause a memory allocation error that would result in the failure of the IIS service. Exchange 2000 is affected by the same vulnerability. To support web-based mail clients, it introduces the ability to address items on the store via URLs. This is done in part by using IIS 5.0, and in part via code that is specific to Exchange 2000. Both pieces of code contain the flaw, but the effect of exploiting the vulnerability via either would be the same -- it could be used to cause the IIS service to fail, but could not be used to attack the Exchange service itself. That is, successfully attacking an Exchange server via this vulnerability would disrupt web-based mail clients' use of the server, but not that of MAPI-based mail clients like Outlook. Because the flaw occurs in two different code modules, one of which installs as part of IIS 5.0 and both of which install as part of Exchange 2000, it is important for Exchange 2000 administrators to install both the IIS and Exchange patches. Mitigating Factors: ==================== - The vulnerability would not enable the attacker to gain any administrative control over the server, or to alter any data on it. - The affected services automatically restart in the event of a failure, so an affected system would resume service almost immediately. - A successful attack against an Exchange server would only disrupt web-based mail clients' use of the server. The server would continue to be available for MAPI-based clients like Outlook. - The ISAPI involved in this vulnerability authenticates the user prior to servicing the request, so a properly configured Exchange server would be at less risk than an IIS server. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-014.asp for information on obtaining this patch. Acknowledgment: =============== - Kevin Kotas of eSecurityOnline.com (http://eSecurityOnline.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. - -----BEGIN PGP SIGNATURE----- Version: PGP Personal Privacy 6.5.3 iQEVAwUBOp7Bvo0ZSRQxA/UrAQF/vQf/VsWFCxqBc0ssPzieJh8pcJWsNyKh32Yf Q2tcKXp1dwNYAGwfMqa6CBDO3FjFih5c82g5wDoNoPMCUJjsZvGAlZW1wKUqu1+t tyRltK27FkxjfoLFYC5YCIEvO6qCDU5lxKUoK0IiEmIyqWakSc9PYLSNRwlxXAUH CJPa2Ad/0Io6hLdFc+jtXxdx/UQofZ8kNycLDiK6IMBmqyYqhX+YrMMqXxYGpJp7 oK1mAvf5mTOtDLmRpzAMbYoFp5a1pYgA89j0e1+4EFBV9lz9aKCk12e9HIw1i8hS bMXVhIhNtxzQHxnkV5einH3H99o7GUJbNhAuQhzBwIYSHQOrQxNrsQ== =nphg - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBOp+tiSh9+71yA2DNAQFhcwQAiRQWErNa08eBw0+x7TDIT3BP6NZB5OVQ UMPdetDsh1E01sm5oR7fLEdW2NI299l7OQajyQ1i8Ha5UHggGLovXHOyiSEiMivJ iaK0CQLlnaB6Ty2CDmnk3axEd3HjX2zKVCrrw5wy1qJlIrLVyLypfyXI87xJ4mhh wgbox5yx1vE= =letU -----END PGP SIGNATURE-----