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Vulnerability Note VU#821420Cisco IOS fails to properly handle summary packets in the VLAN Trunking ProtocolOverviewCisco IOS fails to properly handle summary packets in the VLAN Trunking Protocol. This vulnerability may allow a remote, unauthenticated attacker to cause a denial-of-service condition.I. DescriptionCisco's VLAN Trunking Protocol (VTP) provides the ability to manage the addition, deletion, and renaming of Virtual Local Area Networks (VLANs) across an entire network. VTP is supported on a number of different Cisco products in both the IOS and CatOS operating systems. According to Cisco Systems:When a switch receives a specially crafted summary packet, the switch will reset with a Software Forced Crash Exception. Messages for either "watchdog timeout" or "CPU hog" for process VLAN Manager will be seen prior to the software reset within the syslog messages generated by the switch. The packets must be received on a trunk enabled port. Note that this vulnerability affects Switches and Ethernet Switch Modules for Cisco 1800/2600/2800/3600/3700/3800 Series Routers running Cisco IOS software that have VTP Operating Mode as either "server" or "client". See Cisco Security Response cisco-sr-20060913-vtp for more detailed version information. Switches running CatOS and those configured with VTP operating mode as "transparent" are not affected by this vulnerability II. ImpactA remote, unauthenticated attacker may be able to cause a denial of service condition.III. SolutionUpgrade IOSFor details on fixes, and updates, please see Cisco Security Response cisco-sr-20060913-vtp.
References
This issue was reported in Cisco Security Response cisco-sr-20060913-vtp. Cisco credits FX of Phenoelit for reporting this issue. This document was written by Chris Taschner.
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