full-disclosure - Re: Cisco IOS Denial of Service that affects most Cisco IOS routers- requires power cycle to recover

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Message-ID: <OF3CEF1AEC.3A70C7BB-ON85256D6A.00771B34@tco.census.gov>
From: lee.e.rian at census.gov (lee.e.rian@...sus.gov)
Subject: 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                                                                                               
                      <rdump@...er.com>        To:       incidents@...urityfocus.com                                                
                                               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.4.53.0307172223150.11409@...annon.precision-guesswork.com>,
 Tina Bird <tbird@...cision-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

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