oss-security - Re: CVE Request -- vsftpd -- Do not create network namespace per connection

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Message-ID: <4DED6072.40403@redhat.com>
Date: Tue, 07 Jun 2011 07:19:14 +0800
From: Eugene Teo <eugene@...hat.com>
To: oss-security@...ts.openwall.com
CC: Jan Lieskovsky <jlieskov@...hat.com>,
        "Steven M. Christey" <coley@...us.mitre.org>,
        Chris Evans <scarybeasts@...il.com>, Greg KH <greg@...ah.com>,
        Kees Cook <kees@...ntu.com>
Subject: Re: CVE Request -- vsftpd -- Do not create network
 namespace per connection

On 06/07/2011 12:19 AM, Jan Lieskovsky 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:
> [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.
> 
> Though not sure, how it would be wrt to CVE identifier(s) assignment.
> 
> Steve, could you advice here?

It is worth noting that for a local, unprivileged user to trigger this,
they will need to have the CAP_SYS_ADMIN capability. So this limits the
attack to some services like vsftpd. I see this more of a kernel issue
as configuring vsftpd to set isolate_network=NO is not a long-term solution.

Thanks, Eugene

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