Cisco & Microsoft Patch TCP Stack DoS Exploit

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A fairly serious flaw that was announced in October 2008 by Outpost24 (and apparently discovered way back in 2005), has finally been patched by the major players Cisco and Microsoft.

So far Redhat has offered a workaround for the flaw and Juniper has responded that their equipment is not vulnerable.

It could be that Juniper doesn’t really understand the attack yet, if so that’s bad news as most of the Internet backbone (ISP Level) runs on Juniper equipment.

Microsoft and Cisco have issued updates that protect against a new class of attack that requires very little bandwidth and can leave servers and routers paralyzed even after a flood of malicious data has stopped.

The bug in the TCP, or transmission control protocol, was disclosed in October by security researchers Jack Louis and Robert E. Lee of Sweden-based Outpost24. It gave many security watchers pause because it provided attackers with a new way to launch potentially crippling attacks on a wide array of equipment used to route traffic over the internet.

“This is definitely momentum and other vendors, once they fully understand what has been talked about here, will come up with mitigation strategies of their own,” Lee told The Register. “This really is good progress from both Microsoft and Cisco.”

Microsoft rolled it out in their normal “Patch Tuesday” fashion and Cisco issued a bulletin about especially disruptive DoS attacks.

Good to see it being addressed finally, I guess it took Microsoft some time and money in R&D to come up with a satisfactory solution.

I wonder if any other vendors will be following suite shortly.

On Tuesday, Microsoft responded with MS09-048, a security advisory that fixes a variety of networking vulnerabilities in Windows operating systems, including those discovered by Louis and Lee. The update implements a new feature called memory pressure protection, which automatically drops existing TCP connections and SYN requests when attacks are detected.

The update from Microsoft came during the company’s Patch Tuesday, in which it fixed a total of eight security vulnerabilities in various versions of its Windows operating system. In all, Microsoft issued five patches, which change the way Windows processes javascript, MP3 audio files and wireless signals. As always, the Sans Institute provides a helpful overview here.

Cisco issued it’s own bulletin warning that multiple products are vulnerable to DoS, or denial-of-service attacks that can be especially disruptive.

It’s often hard to fix problems like this in core components because a band-aid solution could end up breaking some of the functionality, especially with something like the TCP stack which is relied on so heavily.

Even then, a patch is released but how many people actually apply it? Cisco equipment is well known for being hard to manage/patch so I’d imagine many network devices will remain unpatched.

Source: The Register