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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2002.602 -- Microsoft Security Bulletin MS02-063 Unchecked Buffer in PPTP Implementation Could Enable Denial of Service Attacks (Q329834) 01 November 2002 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Remote Access Services (RAS) Vendor: Microsoft Operating System: Windows 2000 Windows XP Impact: Denial of Service Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- - - ---------------------------------------------------------------------- Title: Unchecked Buffer in PPTP Implementation Could Enable Denial of Service Attacks (Q329834) Date: 30 October 2002 Software: Windows 2000, Windows XP Impact: Denial of Service Max Risk: Critical Bulletin: MS02-063 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS02-063.asp. - - ---------------------------------------------------------------------- Issue: ====== Windows 2000 and Windows XP natively support Point-to-Point Tunneling Protocol (PPTP), a Virtual Private Networking technology that is implemented as part of Remote Access Services (RAS). PPTP support is an optional component in Windows NT 4.0, Windows 98, Windows 98SE, and Windows ME. A security vulnerability results in the Windows 2000 and Windows XP implementations because of an unchecked buffer in a section of code that processes the control data used to establish, maintain and tear down PPTP connections. By delivering specially malformed PPTP control data to an affected server, an attacker could corrupt kernel memory and cause the system to fail, disrupting any work in progress on the system. The vulnerability could be exploited against any server that offers PPTP. If a workstation had been configured to operate as a RAS server offering PPTP services, it could likewise be attacked. Workstations acting as PPTP clients could only be attacked during active PPTP sessions. Normal operation on any attacked system could be restored by restarting the system. Mitigating Factors: ==================== - As discussed in more detail in the FAQ, Microsoft has only successfully demonstrated denial of service attacks via this vulnerability. Because of how the overrun occurs, it does not appear that that there is any reliable means of using it to gain control over a system. - Servers would only be at risk from the vulnerability if they had been specifically configured to offer PPTP services. PPTP does not run by default on any Windows system. Likewise, although it is possible to configure a workstation to offer PPTP services, none operate in this capacity by default. - Exploiting the vulnerability against a PPTP client could be difficult. PPTP is typically used in scenarios in which the client IP address changes frequently (e.g., because the client system is mobile). Not only would an attacker need to learn the IP address, but he or she would also need to mount an attack while the client had an active PPTP session underway. Risk Rating: ============ - Internet systems: Critical - Intranet systems: Low - Client systems: Low Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin at http://www.microsoft.com/technet/security/bulletin/ms02-063.asp for information on obtaining this patch. - - --------------------------------------------------------------------- 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 7.1 iQEVAwUBPcA8vI0ZSRQxA/UrAQHluwf/dmVnInaVNLy69X2DKk6+NYWRnl+9NC1S rVmUSsth8YtHVCseV966cVR+vom42gnovH0PChT9V9iOZCGvkZywpLcqsWeFNz5+ eJxaOxJqVGGDuXdabdENkONjL0Tz2LDGQr7L4CFDGMB36fmQVuIaYmeW+ZSKR/yQ cKezKO6yIlHlK2KJRQZt6KvSPxlNX0B8InjpfrYg8OI41VSdAjy7+gqxlKE0++sC Rgji08qDsy9xjf3e7lkzmF1Turt0fZqlFLF1IuqLpim8onnG8ibtYxsiY1IZkDbG /h5p+PqUCjCIP9ZqBSWNctGo9zYKiu8dlM4VNogJGk2C4jHF6y6Asg== =2BP7 - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. 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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 member emergencies only. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBPcJrAih9+71yA2DNAQFovwQAjFciKe2CxisL2j/gzWrDJx9RjkYxfBCF KdrAow3PIEZtKA0h3oVVrshkKBPkm0cbnxO6i9ch5LdGu2nLA1xclV6HjzT/W16L sdPUUeZQgldxP+2s+kD91GilTj4N8CyT2mvolGmzJQUeDCqUOeFc0LhbLRi1XP7r PXbObdDlSXg= =UZqf -----END PGP SIGNATURE-----