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Date: Fri, 2 Mar 2018 04:58:50 -0700
From: Kurt Seifried <>
To: oss-security <>
Subject: Re: memcached UDP amplification attacks

On Fri, Mar 2, 2018 at 4:44 AM, Hanno Böck <> wrote:

> Hi,
> In the past days there have been reports about some DDoS attacks
> abusing the memcached UDP protocol:
> port-11211/
> The issue: memcached has an UDP protocol that allows getting a much
> larger reply than the query sent, thus allowing amplification attacks
> with forged sender IPs.
> Upstream memcached reacted by disabling the UDP-based protocol by
> default:
> This is good, however one could argue that they should also default to
> localhost only.
> Most distros I checked right now default to enabling UDP, but
> restricting connections to While this is not directly
> vulnerable it's only a minor change away from being so. The memcached
> announcement sounds like the UDP protocol is rarely used and should be
> considered deprecated and replaced by the TCP-based one.
> I recommend all distributions consider changing their defaults to
> disabling the UDP-based memcached protocol by default.
I think in general ALL network applications that support UDP need to think
about hardening their default configurations due to the potential for
amplification attacks.

While it is not yet CVE worthy I can see the bar moving (much like it has
for default passwords, and crypto) in the near future as this is clearly
becoming a problem. Please note that this problem is already covered by
CWE-406 (to some degree) which makes the case for CVE assignment stronger.

> --
> Hanno Böck
> mail/jabber:
> GPG: FE73757FA60E4E21B937579FA5880072BBB51E42


Kurt Seifried -- Red Hat -- Product Security -- Cloud
PGP A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
Red Hat Product Security contact:

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