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Cisco patches OSPF bug that sends traffic into black holes

If the NSA had known about this flaw it would never have needed backdoors

Cisco has shipped a patch for a buggy Open Shortest Path First (OSPF) routing implementation it says offers exploits that include traffic blackholing or interception.

As the advisory notes, the vulnerability “could allow an unauthenticated attacker to take full control of the OSPF Autonomous System (AS) domain routing table, blackhole traffic, and intercept traffic”, which makes El Reg wonder why the NSA ever had to go to the alleged bother of intercepting hardware for to allegedly install its compromises.

Crafted OSPF packets can be sent to devices running the faulty code, and those packets would make the targeted router flush its routing table. A crafted OSPF Link State Advertisement (LSA) type 1 update can then be propagated through a targeted domain.

As Cisco notes, OSPF is designed for managing traffic within an Autonomous System – think of it as an enterprise routing protocol, rather than for links between service providers. OSPF looks for the “best” route between source and destination by building a database of link states, and using that topology for routing decisions.

The eavesdropping potential arises because an attacker might be able to inject false routes into a network – including, for example, an instruction that the attacker gets to see the traffic before sending it onwards.

Cisco notes that “an attacker must accurately determine certain parameters within the LSA database on the target router. This vulnerability can only be triggered by sending crafted unicast or multicast LSA type 1 packets. No other LSA type packets can trigger this vulnerability.”

The bug affects “all unfixed versions of Cisco IOS Software, Cisco IOS XE Software, Cisco ASA Software, Cisco PIX Software and Cisco FWSM Software”. ®

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