Cisco Systems Inc. Affected

Updated:  July 29, 2001



Vendor Statement

-----BEGIN PGP SIGNED MESSAGE----- Cisco Security Advisory: Cisco IOS PPTP vulnerability Revision 1.0 For Public Release 2001 July 12 08:00 (UTC -0800) Summary Point to Point Tunneling Protocol (PPTP) allows users to tunnel to an Internet Protocol (IP) network using a Point to Point Protocol (PPP). The protocol is described in RFC2637. PPTP implementation using Cisco IOSĀ® software releases contains a vulnerability that will crash a router if it receives a malformed or crafted PPTP packet. No special conditions or router configuration is required. This vulnerability is present in all Cisco IOS releases that support PPTP protocol. PPTP is supported in the following software releases: * 12.1 train, releases: T, E, EZ, YA, YD and YC * 12.2 train, all releases No other Cisco product is vulnerable. There is no workaround for this vulnerability. This advisory is available at Affected Products This vulnerability is present in all Cisco IOS releases that are supporintg PPTP protocol. PPTP is supported in the following releases * 11.x train does not supports PPTP * 12.1 train, releases: T, E, EZ, YA, YD and YC * 12.2 train, all releases To determine if a Cisco product is running an affected IOS, log in to the device and issue the command show version. Look for the "Internetwork Operating System Software" or "IOS (tm)" information, which also will have a version number. Other Cisco devices either will not have the command "show version" or will give different output. Details By sending a crafted PPTP packet to a port 1723, a control PPTP port, it is possible to crash the router. This vulnerability does not require special router configuration. Enabling PPTP is sufficient to expose the vulnerability. The router will crash after it receives a single packet. This vulnerability is documented as Cisco Bug ID CSCdt46181 Impact By repeaditly exploiting this vulnerability it is possible to cause permanent Denial of Service (DoS). This denial is not only of the PPTP functionality but the whole router will stop functioning. Software Versions and Fixes Each row of the table describes a release train and the platforms or products for which it is intended. If a given release train is vulnerable, then the earliest possible releases that contain the fix and the anticipated date of availability for each are listed in the "Rebuild", "Interim", and "Maintenance" columns. A device running a release in the given train that is earlier the release in a specific column (less than the earliest fixed release) is known to be vulnerable. The release should be upgraded at least to the indicated release or a later version (greater than the earliest fixed release label). When selecting a release, keep in mind the following definitions: Maintenance Most heavily tested and highly recommended release of any label in a given row of the table. Rebuild Constructed from the previous maintenance or major release in the same train, it contains the fix for a specific defect. Although it receives less testing, it contains only the minimal changes necessary to effect the repair. Interim Built at regular intervals between maintenance releases and receive less testing. Interims should be selected only if there is no other suitable release that addresses the vulnerability, and interim images should be upgraded to the next available maintenance release as soon as possible. Interim releases are not available via manufacturing, and usually they are not available for customer download from CCO without prior arrangement with the Cisco TAC. In all cases, customers should exercise caution to be certain the devices to be upgraded contain sufficient memory and that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, contact the Cisco TAC for assistance as shown in the following section. More information on IOS release names and abbreviations is available at | | Description of Image | | Train | or Platform Availability of Fixed Releases* | | 12.1-based Releases | Rebuild |Interim** | Maintenance | | 12.1E |Core/ISP support: GSR, | | | 12.1(8a)E | | |RSP, c7200 | | | | | 12.1EZ |Early Deployment (ED): |12.1(6)EZ2 | | | | |special image | | | | | |Early Deployment(ED): VPN, |Not Scheduled | | 12.1T |Distributed Director, +-------------------------------------+ | |various platforms |Upgrade recommended to 12.2(3) | | | |Not Scheduled | | 12.1YA |Short-lived early +-------------------------------------+ | |deployment release |Upgrade recommended to 12.2(2)XB | | 12.1YC |Short-lived early |12.1(5)YC1 | | | | |deployment release | | | | | 12.1YD |Short-lived early |12.1(5)YD2 | | | | |deployment release |2001-June-25| | | | 12.2-based Releases | Rebuild |Interim** | Maintenance | | 12.2 |General deployment release | |12.2(1.1) |12.2(3) | | |for all platforms | | |2001-August | | 12.2T |General deployment release | | |12.2(4)T | | |for all platforms | | | | | 12.2XA |SPLOB | | |12.2(2)XA | | 12.2XD |Short-lived early |12.2(1)XD1 | | | | |deployment release | | | | | 12.2XE |Short-lived early | | |12.2(1)XE | | |deployment release | | | | | 12.2XH |Short-lived early | | |12.2(1)XH | | |deployment release | | |2001-June-25 | | 12.2XQ |Short-lived early | | |12.2(1)XQ | | |deployment release | | |2001-June-23 | | Notes | | * All dates are estimated and subject to change. | ** Interim releases are subjected to less rigorous testing than regular | | maintenance releases, and may have serious bugs. Obtaining Fixed Software Cisco is offering free software upgrades to eliminate this vulnerability for all affected customers. Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained through the Software Center on Cisco's Worldwide Web site at Customers whose Cisco products are provided or maintained through prior or existing agreement with third-party support organizations such as Cisco Partners, authorized resellers, or service providers should contact that support organization for assistance with the upgrade, which should be free of charge. Customers who purchase direct from Cisco but who do not hold a Cisco service contract and customers who purchase through third party vendors but are unsuccessful at obtaining fixed software through their point of sale should get their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC contacts are as follows: * +1 800 553 2447 (toll-free from within North America) * +1 408 526 7209 (toll call from anywhere in the world) * e-mail: Please have your product serial number available and give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC. Please do not contact either "" or "" for software upgrades. Workarounds There is no workaround for this vulnerability. Exploitation and Public Announcements This vulnerability has been reported to us by a customer. The Cisco PSIRT received a report about potential exploitation of this vulnerability for malicious purpose against one customer. Status of This Notice: INTERIM This is an interim security advisory. Cisco anticipates issuing updated versions of this notice at irregular intervals because there may be material changes in the facts. The reader is warned that this notice may contain inaccurate or incomplete information. Although Cisco cannot guarantee the accuracy of all statements in this notice, all of the facts have been checked to the best of our ability. Cisco anticipates issuing monthly updates of this notice until it reaches FINAL status. Note: A standalone copy or paraphrase of the text of this security advisory that omits the distribution URL in the following section is an uncontrolled copy and may lack important information or contain factual errors. Distribution This notice will be posted on Cisco's Worldwide Web site at In addition to Worldwide Web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients: * * * (includes CERT/CC) * * * * Various internal Cisco mailing lists Future updates of this notice, if any, will be placed on Cisco's Worldwide Web server, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the URL given above for any updates. Revision History Revision 1.0 2001-Jul-12 08:00 UTC -0800 Initial public release Cisco Security Procedures Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's Worldwide Web site at This includes instructions for press inquiries regarding Cisco security notices. All Cisco Security Advisories are available at This notice is Copyright 2001 by Cisco Systems, Inc. This notice may be redistributed freely after the release date given at the top of the text, provided that redistributed copies are complete and unmodified, and include all date and version information. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQEVAwUBO028kWiN3BRdFxkbAQEgHAf+J+FhUoKCGi/L6h6KstLg6L5kOubaCfnW yBh0DYb/YWWRcHl2XGEYhiY66YXAyyrJiXKCoTW/g/eHGnnZLXvKpip+C5qQB/uT o7hQ+CGL8SrGq+j1adogDAaim4FfXLUGmD7N6/SOdeDi9nr8DNhyH9SrAouVvA1V syh/IwNy+8MTBvAlrbPgwoP6TLK6NC3Go1aruJyTvT955jZcPbIY2UNHwzl9TU0x uf9+jrWOfNho+02K4Yzz2BJSXy1XQ+Hk4fnQTC3g55FjyxrQZvhwhR1KC/fJp8kF o/aoOjgtSIVtSS9bjVxiNtz9t6aE6PLnvj3dNiORol6IWFKM8W/r3g== =6V7h -----END PGP SIGNATURE-----

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


The CERT/CC has no additional comments at this time.