Published:
14 March 2001
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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2001.116 -- Microsoft Security Bulletin MS01-016 (version 2.0) Malformed WebDAV Request Can Cause IIS to Exhaust CPU Resources 15 March 2001 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: IIS 5.0 Vendor: Microsoft Impact: Denial of Service Access Required: Remote Ref: ESB-2001.107 - --------------------------BEGIN INCLUDED TEXT-------------------- The following is a Security Bulletin from the Microsoft Product Security Notification Service. Please do not reply to this message, as it was sent from an unattended mailbox. ******************************** - -----BEGIN PGP SIGNED MESSAGE----- - - -------------------------------------------------------------------- Title: Malformed WebDAV Request Can Cause IIS to Exhaust CPU Resources Released: 08 March 2001 Revised: 13 March 2001 (version 2.0) Software: IIS 5.0 Impact: Denial of Service Bulletin: MS01-0016 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS01-016.asp - - -------------------------------------------------------------------- Reason for Revision: ==================== The original version of this bulletin provided a workaround (discussed in Knowledge Base article Q241520) that would protect affected systems by disabling WebDAV services. However, a security patch is now available that eliminates the vulnerability, and Microsoft recommends using the patch rather than the workaround. We have updated both the bulletin and the narrative below to reflect this. Issue: ====== WebDAV is an extension to the HTTP protocol that allows remote authoring and management of web content. In the Windows 2000 implementation of the protocol, IIS 5.0 performs initial processing of all WebDAV requests, then forwards the appropriate commands to the WebDAV process. However, a flaw exists in the way WebDAV handles a particular type of malformed request. If a stream of such requests were directed at an affected server, it would consume all CPU availability on the server. The patch should be applied to all machines running IIS 5.0. While this obviously includes web servers, it's worth noting that IIS 5.0 may be running on other types of servers as well, particularly mail servers running Exchange 2000. Mitigating Factors: ==================== - The effect of an attack via this vulnerability would be temporary. The server would automatically resume normal service as soon as the malformed requests stopped arriving. - The vulnerability does not provide an attacker with any capability to carry out WebDAV requests. - The vulnerability does not provide any capability to compromise data on the server or gain administrative control over it. Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin http://www.microsoft.com/technet/security/bulletin/ms01-016.asp for information on obtaining this patch. - - ------------------------------------------------------------------- - -----BEGIN PGP SIGNATURE----- Version: PGP Personal Privacy 6.5.3 iQEVAwUBOq7jso0ZSRQxA/UrAQF1QwgAlgv97QgEKhq/VR39SSQTzq4nEgvj0XFy jWrxuIwFlOKiIVFV61Tjjip7HSex1OgZF4UD1EafPeNcNmE+A157Ufk3/QeQXzxO dY0AF/cvSlGvBOk52Pw/RgYPbpez8/dAzgabz7vyDDm6zL1gqX7SKqNnzPEnldzy 8gB17X5KMduRdDSqTW7Rf09lFd9covzSZNGIDLnfzjBQiuA9UilgxxaDarfBrf67 lZ1oTjmdH1MRC39ki/p8ye0T5LSMT3AIRVCLFaJmqtOLoBV5bCIMpc1DtJhJJNqq t3uCTi0fCcWLxLvGucix+/a0INxJtF2CZCxPoPkn6yHB92rwYBgQ4w== =YUwQ - -----END PGP SIGNATURE----- ******************************************************************* You have received this e-mail bulletin as a result of your registration to the Microsoft Product Security Notification Service. 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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 iQCVAwUBOrCfrSh9+71yA2DNAQHA4AP9FPwlnZqZklyrOMsdsmg8tuBnoDAdQzQz SDrDNxaEBymatz6O7zsGxPphRENokq+QDuZZJZPdV6MWlsN6LpW6evOTPqTyQ1cc 5eFIigFXpz/HtAfNf7GGd2AFe6NPg2wz4KelUF2cjKq6EKStarUiJptnmwS7kEK9 ql65NbGNGLo= =TkJP -----END PGP SIGNATURE-----