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0005 2000/01/22 Ascend ISDN Router DoS vulnerability (old UDP echo problem)
==== TESO Informational =======================================================
This piece of information is to be kept confidential.
===============================================================================
Description ..........: Ascend ISDN Router DoS vulnerability
Date .................: 2000/01/22 21:00
Author ...............: scut
Publicity level ......: known
Affected .............: unfirewalled Ascend ISDN Routers, for example Ascend
Pipeline 50 routers
Type of entity .......: Router
Type of discovery ....: denial of service attack
Severity/Importance ..: interesting
Found by .............: hendy and scut
Information ===================================================================
A standard Ascend ISDN router has the UDP echo port open. By spoofing the
source IP address as the destination IP address of the router and sending a UDP
packet to the router the router will keep the packet within it's internal
packet table forever. However this is a very old denial of service attack, but
it has some nice effects here.
For example by sending packets of 500 bytes length you can constantly increase
the generic router delay time from 0 ms to up to 800 ms. After that the router
packet table is completely overflowed and the router is inoperational. In this
state the only thing that will help is a hard reset of the router.
This is just the old echo/echo UDP link problem, but still living very happily
in any Ascend ISDN router.
===============================================================================
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