If the packet expires in transit i.e. ttl 1 to router 2 hops away means it never gets to that router. Not possible to fill a queue with a packet that is dropped by the previous router. Check out "Internet Core Protocols" at Oreilly. Curt Purdy CISSP, GSEC, MCSE+I, CNE, CCDA Information Security Engineer DP Solutions cpurdyat_private 936.637.7977 ext. 121 ---------------------------------------- If you spend more on coffee than on IT security, you will be hacked. What's more, you deserve to be hacked. -- White House cybersecurity adviser Richard Clarke -----Original Message----- From: full-disclosure-adminat_private [mailto:full-disclosure-adminat_private]On Behalf Of lee.e.rianat_private Sent: Monday, July 21, 2003 4:55 PM To: rnewsat_private Cc: incidentsat_private; full-disclosureat_private Subject: [Full-Disclosure] Re: Cisco IOS Denial of Service that affects most Cisco IOS routers- requires power cycle to recover > The kickup to supervisor level happens when the packet is targeted > directly at the router's IP address (per first Cisco advisory) or just > has its TTL expire in transit past the router (per revised Cisco > advisory). Has anyone been able to verify that the problem occurs when the TTL expires "in transit"? I've been able to get packets stuck on the input queue by sending to the router's interface address, sending to <network, 0> and <network, -1> but sending to a router two hops away with a TTL of 1 just gives me an icmp ttl exceeded & nothing new stuck on the input queue. Lee Richard Johnson <rdumpat_private> To: incidentsat_private cc: 07/20/2003 03:20 Subject: Re: Cisco IOS Denial of Service that affects most Cisco IOS routers- AM requires power cycle to recover Please respond to rnews In article <Pine.BSO.4.53.0307172223150.11409at_private-guesswork.com>, Tina Bird <tbird@precision-guesswork.com> wrote: > information on the detailed structure of the evil packets in these > protocols is not yet public AFAIK. The router has problems if it receives a packet, content irrelevant, that makes it to supervisor level claiming an IP protocol that it doesn't have code to handle. The kickup to supervisor level happens when the packet is targeted directly at the router's IP address (per first Cisco advisory) or just has its TTL expire in transit past the router (per revised Cisco advisory). Send enough packets (default 75), and the input queue is full. hping is enough of a launch platform for that--there's no need for questionable-source exploit binaries when testing. Richard -- My mailbox. My property. My personal space. My rules. Deal with it. http://www.river.com/users/share/cluetrain/ --------------------------------------------------------------------------- ---------------------------------------------------------------------------- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html --------------------------------------------------------------------------- ----------------------------------------------------------------------------
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