Cisco Security Advisory
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AV:R/AC:L/Au:NR/C:N/I:N/A:C/B:N/E:U/RL:O/RC:C
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Cisco IOS contains a vulnerability in the VLAN Trunking Protocol (VTP) that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists because the VTP feature in several versions of Cisco IOS software does not properly handle malformed packets sent from the local network. An attacker residing on the local network segment could exploit this vulnerability via a crafted summary packet to cause a DoS condition.
Cisco has confirmed this vulnerability in a security advisory and released updated software to correct it.
To exploit this vulnerability, an attacker must reside on the local network segment and send a crafted summary packet to a device supporting VTP. The device must be configured as either client or server for VTP. Additionally, the packets must be received on a trunk enabled port. Switches configured with a VTP domain password are still affected.
The switch receiving the packet generates syslog messages for either watchdog timeout or CPU hog for process VLAN Manager prior to the software reset. Exploitation causes a DoS condition only until the device reboots. Repeated attacks could cause an extended DoS condition.
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Cisco has released a security response regarding Cisco Bug IDs CSCsd52629 (registered users) and CSCsd34759 (registered users) at the following link: cisco-sr-20060913-vtp
Vulnerable Products
Cisco IOS devices having VTP Operating Mode as either server or client are vulnerable.
A complete list of affected IOS products is available for registered users at the following link: Cisco
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by these vulnerabilities.
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Administrators are advised to apply the appropriate software updates.
Administrators are advised to restrict access to affected devices.
Administrators are advised to protect the local area network from external attacks with a strong firewall implementation.
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Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at tac@cisco.com.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.0 Initial Release NA Final 2006-Sep-13
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