Networks on yellow alert over ICMP flaw

Industry reels from IP bug

By John Leyden, 14th April 2005

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ISPs and enterprises were this week advised to update their internet communications infrastructure following the discovery of a vulnerability affecting a raft of major suppliers including Cisco, Juniper, Microsoft and IBM to varying degrees.

Security researchers have discovered that multiple TCP/IP implementations fail to adequately validate Internet Control Message Protocol (ICMP) error messages. As a result, hackers could reset or slow an established connection using spoofed ICMP error messages.

Applications that depend on long-lived, low latency or high throughput TCP connections would be particularly affected by such an attack. In order to spoof an ICMP message, an attacker would need to know or guess the source and destination TCP port. Security clearing house US CERT warns that Border Gateway Protocol (BGP) transmissions fall into both these categories and are therefore most at risk from attack. Such an attack would be far from trivial to mount but could have devastating consequences.

BGP is used to provide critical routing information. A sustained attack targeting vulnerable routers running the protocol may create ongoing net degradation, US CERT warns. A list of affected suppliers, with links to security notices where available, can be found here.

Network administrators are advised to upgrade or apply a patch (where available). Alternatively users can try to filter ICMP messages as a workaround. The UK National Information Security Co-ordination Centre has published a UNIRAS alert on the vulnerability here. ®