Published:
01 October 2001
Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.407 -- Microsoft Security Bulletin MS01-049 Deeply-nested OWA Request Can Consume Server CPU Availability 2 October 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Exchange 2000 Vendor: Microsoft Impact: Denial of Service Access Required: Existing Account Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- - - ---------------------------------------------------------------------- Title: Deeply-nested OWA Request Can Consume Server CPU Availability Date: 26 September 2001 Software: Exchange 2000 Impact: Denial of Service Bulletin: MS01-049 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-049.asp. - - ---------------------------------------------------------------------- Issue: ====== A security vulnerability exists in Exchange 2000 Outlook Web Access, because it will accept and process a request for an item in an authenticated user's mailbox without verifying first that the folder structure is valid. An attacker could mount a denial of service attack by repeatedly levying a request for a non-existent but deeply nested folder in his own mailbox. Exploiting the vulnerability wouldn't necessarily affect the OWA server itself. The effect of the vulnerability would be to cause the process servicing the attacker's mailbox to consume most or all of the CPU availability on the server it was running on. In may cases, this process would run on the OWA server, and thus the effects would be seen there. However, if the process servicing the attacker's mailbox ran on a back-end server, the effect of exploiting the vulnerability would be seen there. In any event, the affected server would resume normal service once the request was handled. Mitigating Factors: ==================== - Only users who could authenticate to the server could exploit this vulnerability. - The attacker would need to have permissions on at least one mailbox in order to exploit the vulnerability. - The user can only perform this task against mailboxes to which they have permission. - The vulnerability could not be used to cause the mailbox store to fail, or to corrupt mailbox data. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin at http://www.microsoft.com/technet/security/bulletin/ms01-049.asp for information on obtaining this patch. Acknowledgment: =============== - Joao Gouveia (tharbad@kaotik.org) - - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. 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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 iQCVAwUBO7mliSh9+71yA2DNAQGCGwP8Dj/i+fHdjaddS5CLcp40JUWMfSxAAU2k RT4FDO+K2vNSQKL453uPhsyrAkyfRnnc1fLxB8ybsOTS6nXhQubwKEe3tSLwr4Dr +uvLuhFvQgDBy8QcGu8u3n0d1ddseqAg8vggMPC59OaKMB/rTieEiOl4UxMvusW+ LnKgJqIXybA= =TEFF -----END PGP SIGNATURE-----