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Date: Wed, 7 Mar 2018 07:20:47 -0700
From: Kurt Seifried <kseifrie@...hat.com>
To: Tomas Hoger <thoger@...hat.com>
Cc: Kurt Seifried <kseifried@...hat.com>, oss-security@...ts.openwall.com
Subject: Re: memcached UDP amplification attacks

Actually the 50k was based on a private but trustworthy reporter (The 3 letter agency people), some people store very big things in memcached like cached web pages...

> On Mar 7, 2018, at 3:09 AM, Tomas Hoger <thoger@...hat.com> wrote:
> 
>> On Fri, 2 Mar 2018 21:42:30 -0700 Kurt Seifried wrote:
>> 
>> I have assigned CVE-2018-1000115 to this issue:
>> 
>> Memcached version 1.5.5 contains an Insufficient Control of Network
>> Message Volume (Network Amplification, CWE-406) vulnerability in the
>> UDP support of the memcached server that can result in denial of
>> service via network flood (traffic amplification of 1:50,000 has been
>> reported by reliable sources). This attack appear to be exploitable
>> via network connectivity to port 11211 UDP. This vulnerability
>> appears to have been fixed in 1.5.6 due to the disabling of the UDP
>> protocol by default.
> 
> Minor nitpick, the description mentions 1:50,000 ratio, apparently
> based on the information in the following reference:
> 
>> https://blogs.akamai.com/2018/03/memcached-fueled-13-tbps-attacks.html
> 
> where it's mentioned as:
> 
> """
> Worse, memcached can have an amplification factor of over 50,000,
> meaning a 203 byte request results in a 100 megabyte response.
> """
> 
> However, 200 * 50k = 10m, not 100m.  Wonder if I'm doing my math wrong.
> 
> -- 
> Tomas Hoger / Red Hat Product Security

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