Secunia

David Barroso Berrueta and Alfredo Andres Omella have reported a vulnerability in Cisco IOS, which can be exploited by malicious people to cause a DoS (Denial of Service).

The vulnerability is caused due to an unspecified error when handling certain malformed VLAN Trunking Protocol (VTP) packets. This can be exploited to cause a device to reload by sending a specially crafted VTP packet.

Successful exploitation requires knowledge of the VTP domain name and the port that is configured for trunking.

The vulnerability is reported in the following devices:
* Cisco 2900XL Series Switches
* Cisco 2950 Series Switches
* Cisco 2955 Series Switches
* Cisco 3500XL Series Switches
* Cisco 3550 Series Switches
* Cisco 3570 Series Switches

Solution
The vendor recommends allowing only trusted devices to connect to ports configured for ISL or 802.1q trunking.

Provided and/or discovered by
Alfredo Andres Omella and David Barroso Berrueta, S21SEC

Original Advisory
Cisco Advisory:
http://www.cisco.com/en/US/products/products_security_response09186a00807d1a81.html

21SEC Advisory:
http://www.s21sec.com/es/avisos/s21sec-034-en.txt

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