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Date: Mon, 6 Jun 2011 10:14:13 -0700
From: Chris Evans <scarybeasts@...il.com>
To: oss-security <oss-security@...ts.openwall.com>
Cc: "Steven M. Christey" <coley@...us.mitre.org>, Greg KH <greg@...ah.com>, Kees Cook <kees@...ntu.com>
Subject: Re: CVE Request -- vsftpd -- Do not create network namespace per connection

On Mon, Jun 6, 2011 at 9:19 AM, Jan Lieskovsky <jlieskov@...hat.com> wrote:

> Hello, Josh, Steve, vendors,
>
>  It was found that vsftpd, Very Secure FTP daemon, when the network
> namespace (CONFIG_NET_NS) support was activated in the kernel, used to
> create a new network namespace per connection. A remote attacker could
> use this flaw to cause a memory pressure and denial of the vsftpd
> service.
>
> References:
> [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=629373
> [2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/720095
> [3] https://bugzilla.redhat.com/show_bug.cgi?id=711134
>
> This one being a bit tricky one -- from my understanding of the issue,
> vsftpd doesn't necessarily have a security flaw on its side. It's
> kernel issue / bug, which allows this to be used for vsftpd DoS:
>

Yes, I will be considering this a kernel issue.
vsftpd also uses one (or more!) process per connection. I'd have though that
a process structure plus stack etc. would be a lot more heavyweight than an
empty network namespace, but obviously not :)

[4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/720095/comments/31
> [5]
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/720095/comments/32
>
> Short-term solution would be probably to address this on the vsftpd
> side, the long-term one then being to get this fixed in kernel.
>

It's actually configurable in vsftpd.conf:
isolate_network=NO

So for a short term fix, all you need is to deploy that config change.
Looking at the Changelog, network isolation was added in vsftpd-2.2.0, and
the config setting has been there from v2.2.0 as well.


Cheers
Chris


> Though not sure, how it would be wrt to CVE identifier(s) assignment.
>
> Steve, could you advice here?
>
> Thank you & Regards, Jan.
> --
> Jan iankko Lieskovsky / Red Hat Security Response Team
>

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