Cisco Cisco IOS Software Release 12.4(2)XB6 Notas de publicación

Caveats describe unexpected behavior or defects in the Cisco IOS software releases. Severity 1 caveats 
are the most serious caveats, severity 2 caveats are less serious, and severity 3 caveats are the 
least serious of these three severity levels.

Caveats in Cisco IOS Release 12.4(11)T are also in Release 12.4(11)XV. For information on caveats in 
Cisco IOS Release 12.4(11)T, refer to the 

document. This 

document lists severity 1 and 2 caveats; the documents are located on 

If you have an account with 

, you can also use the Bug Toolkit to find select caveats of any 

severity. To reach the Bug Toolkit, log in to 

, to go to: 

This sections contains the following information:

There are no open caveats in this release.

CSCse56501

A device running Cisco IOS software that has Internet Protocol version 6 (IPv6) enabled may be 
subject to a denial of service (DoS) attack. For the device to be affected by this vulnerability the 
device also has to have certain Internet Protocol version 4 (IPv4) User Datagram Protocol (UDP) 
services enabled. To exploit this vulnerability an offending IPv6 packet must be targeted to the 
device. Packets that are routed throughout the router can not trigger this vulnerability. Successful 
exploitation will prevent the interface from receiving any additional traffic. The only exception is 
Resource Reservation Protocol (RSVP) service, which if exploited, will cause the device to crash. 
Only the interface on which the vulnerability was exploited will be affected.

Cisco is providing fixed software to address this issue. There are workarounds available to mitigate 
the effects of the vulnerability.

This advisory is posted at