[ISN] Multiple flaws in Cisco router software exposed

From: InfoSec News (isnat_private)
Date: Wed May 23 2001 - 16:15:47 PDT

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    By John Leyden
    Posted: 23/05/2001 at 13:10 GMT
    Cisco Systems has warned that multiple vulnerability with the
    operating system used by its 600 series routers leave its vulnerable
    to a barrage of attacks.
    Late last night, Cisco issued an alert which admitted that 600 series
    routers was subject to not one, not two, not three but four
    potentially serious flaws. It advised users to upgrade the software.
    One flaw with Cisco CBOS Software, which runs on 600 series routers,
    means that passwords are stored in clear text in the memory of a
    If that doesn't take the fancy of crackers they may be interested to
    learn that when multiple, large ECHO REPLY packets are routed through
    an affected Cisco 600 router it will stop passing any further traffic.
    If denial of service attacks are not to the taste of the s'kiddie in
    question perhaps he might care to partake in a spot forgery. Another
    CBOS bug makes it possible to make a successful prediction of TCP
    Initial Sequence Numbers.
    This makes it possible for crackers to modify or intercept traffic
    that either originates at or terminates at a 600 series device, but
    doesn't affect traffic flowing through a router in transit between two
    other points.
    Not good - and there's more.
    The last flaw means a Cisco 600 router may stop passing traffic or
    responding to a console when an ECHO REQUEST packet with the record
    route option is sent through it. It's just as well exploits that
    involve breaking router security are generally beyond the expertise of
    most s'kiddies.
    The solution to all these problems is to upgrade from earlier software
    to either of the following CBOS releases: 2.3.9, 2.4.1 and 2.4.2. More
    information on the issue is available here.
    In writing the story we were struck with an odd sense of deja vu.
    Indeed last December, Cisco was forced to admit a similar (though
    different) set of FOUR security flaws that affected 600 series
    In December we speculated as to why Cisco had not issued a seperate
    notice for each vulnerability, since each was different. At the time
    we speculated that Cisco might bunch vulnerability notices together in
    order to encourage users to upgrade their software. Maybe just one
    potentially devastating flaw isn't good enough.
    We still reckon these batch vulnerability notices are a technique used
    by Cisco to migrate users to newer versions of its software that tie
    them even closer to it. Such a move would make great business sense
    and we'd dearly love to quiz Cisco on this.
    Unfortunately Cisco (which has a reputation as having the worst PR of
    any company in IT among UK journalists) hasn't spoken to us for months
    and so we're unlikely to be able to ask them anything. If anyone at
    Borg central is listening: if we offered cash for interviews would it
    make any difference?
    [Cisco's security notice: 
    http://www.cisco.com/warp/public/707/CBOS-multiple2-pub.html ]
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