31 January 2007
Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2007.0065 -- [Cisco] Cisco VTP Vulnerability 31 January 2007 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: VLAN Trunking Protocol Publisher: Cisco Systems Platform: Cisco 2900XL Series Switches Cisco 2950 Series Switches Cisco 2955 Series Switches Cisco 3500XL Series Switches Cisco 3550 Series Switches Cisco 3750 Series Switches Impact: Denial of Service Access: Remote/Unauthenticated Original Bulletin: http://www.cisco.com/warp/public/707/cisco-sr-20070129-vtp.shtml - --------------------------BEGIN INCLUDED TEXT-------------------- http://www.cisco.com/warp/public/707/cisco-sr-20070129-vtp.shtml Cisco Response ============== An issue has been reported to the Cisco PSIRT involving malformed VLAN Trunking Protocol (VTP) packets. This attack may cause the target device to reload, causing a Denial of Service (DoS). Such an attack must be executed on a local ethernet segment, and the VTP domain name must be known to the attacker. Additionally, these attacks must be executed against a switch port that is configured for trunking. Non-trunk access ports are not affected. This issue is tracked as Cisco Bug ID CSCsa67294. Details ======= The VLAN Trunking Protocol (VTP) is a Layer 2 protocol that manages the addition, deletion, and renaming of VLANS on a network-wide basis in order to maintain VLAN configuration consistency. VTP packets are exchanged by VLAN-aware switches. For more information on VTP, consult the following link: http://www.cisco.com/en/US/products/hw/switches/ps663/products_configuration_guide_chapter09186a00800e47e3.html. Upon receiving a malformed VTP packet, certain devices may reload. The attack could be executed repeatedly causing a extended Denial of Service. In order to successfully exploit this vulnerability, the attacker must know the VTP domain name, as well as send the malformed VTP packet to a port on the switch configured for trunking. This does not affect switch ports that are configured for voice vlans. A complete Inter-Switch Link (ISL) or 802.1q trunk port is required for the device to be vulnerable. These platforms are affected: * Cisco 2900XL Series Switches * Cisco 2950 Series Switches * Cisco 2955 Series Switches * Cisco 3500XL Series Switches * Cisco 3550 Series Switches * Cisco 3750 Series Switches No other Cisco products are known to be vulnerable to this issue. This issue was made public on 26-Jan-2007 on the Full-Disclosure and Bugtraq mailing lists. The Cisco bug ID CSCsa67294 was made available to registered customers in May of 2005. We would like to thank David Barroso Berrueta and Alfredo Andres Omella for reporting this vulnerability to us. You can find their release here: http://www.s21sec.com/es/avisos/s21sec-034-en.txt. We greatly appreciate the opportunity to work with researchers on security vulnerabilities and welcome the opportunity to review and assist in security vulnerability reports against Cisco products. Workarounds =========== In order to mitigate your exposure, ensure that only known, trusted devices are connected to ports configured for ISL or 802.1q trunking. More information on securing L2 networks can be found in the Cisco SAFE Layer 2 Security document at this location: http://www.cisco.com/en/US/netsol/ns340/ns394/ns171/ns128/networking_solutions_white_paper09186a008014870f.shtml Additional Information ====================== THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME. Revision History ================ +--------------+------------------+------------------------+ | Revision 1.0 | 2007-January-29 | 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 website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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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 author's website 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/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: firstname.lastname@example.org 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----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBRcARCCh9+71yA2DNAQJB8AP/Zb/AxJ6i6v3O79ac0QZYUJMHtlrYhoEX R1Adw8N3lpJ6LB2pt3Es911pMEP+NyknJC1KpCBkkGKtVS9rLtzBDcelSjdYGcLz KTUOFyUnKsJ7MtroBIV4+O47U4TZ5tCxhHLLgiUdtlx54rTGd9K4y5pTiQUDFHPY QWpFezW81Jc= =vgfm -----END PGP SIGNATURE-----