星期日, 七月 20, 2003
Cisco IOS Vulnerability
Recent Cisco IOS vulnerability has been annonnced as a major problem for the Internet probably affecting every network manager. "By sending specially crafted IPv4 packets to an interface on a vulnerable device, an intruder can cause the device to stop processing packets destined to that interface".
Protocols are protocols[] = { 53, 55, 77, 103 }. They are IP encryption, IP mobility, SUN ND(?) , PIM(Protocol Independent Multicast). A complete list of protocol number assignment is IANA's list.
One has to make sure the sequence of those packets are destined to the Interfact instead of being routed. It is said the hping2 tool can be used like this:
hping2 (dest ip) -0 -t (ttl to make sure packet will hit the interface) -H (53,55,77,103) -d 128 -E /dev/urandom
Somehow the IOS will mistakenly flag the interface as full after processing those packets. Inbound traffic will be dropped accordingly. Cisco's workaround is to use ACL to block those packets to the interface.
Protocols are protocols[] = { 53, 55, 77, 103 }. They are IP encryption, IP mobility, SUN ND(?) , PIM(Protocol Independent Multicast). A complete list of protocol number assignment is IANA's list.
One has to make sure the sequence of those packets are destined to the Interfact instead of being routed. It is said the hping2 tool can be used like this:
hping2 (dest ip) -0 -t (ttl to make sure packet will hit the interface) -H (53,55,77,103) -d 128 -E /dev/urandom
Somehow the IOS will mistakenly flag the interface as full after processing those packets. Inbound traffic will be dropped accordingly. Cisco's workaround is to use ACL to block those packets to the interface.
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