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Date: Tue, 14 Mar 2017 12:17:53 -0400
From: Stiepan <>
To: "" <>, "" <>
Cc: Stéphane Graber <>,
Subject: Re: LXC: CVE-2017-5985: lxc-user-nic didn't verify network namespace ownership

You are welcome. As stated in my reply to Serge H. Hallyn's off-list message, in the meantime I have installed version 2.0.7 from jessie-backports and am unable to reproduce the issue, as I cannot start unprivileged containers anymore (due to a network error). According to Debian's tracker page for lxc, the version that I have installed from backports is 2.0.7-1, which does not include latest upstream fixes. I guess that I have to wait for the 2.0.7-2 package - which includes latest upstream fixes - to land in jessie-backports for these issues (both security and functional) to be fixed.

CC-ing the Debian address for this bug, as they explicitly asked to do this in case there is a need to reopen the Debian bug, which seems to be the case here (at least, for Jessie, since the intermediary 2.0.7-1 .deb apparently breaks unprivileged networking, besides not fixing the security issue).
To the Debian team in charge of this bug:
As unprivileged mode is not activated by default on Debian, I understand that this is not a priority, but it would still be nice to have this fixed quickly.
By the way, not directly related to this specific bug, but I hope that snapd + LXD somehow finds its way into jessie-backports: that would be great!


-------- Original Message --------
Subject: Re: [oss-security] LXC: CVE-2017-5985: lxc-user-nic didn't verify network namespace ownership
Local Time: 14 March 2017 2:06 AM
UTC Time: 14 March 2017 01:07
Stéphane Graber <>,

On 03/10/2017 06:03 AM, Stiepan wrote:
> I don't know whether that is the same bug, or a related one, but on Debian8 using LXC from jessie-backports, setting the default route in a container affects the host - namely, from an unpriv. container, setting the route sets the host's route as well.
> lxc-info --version outputs 2.0.6 and no update is currently available (on Debian).

Thanks for the report. I just tried to reproduce the issue on Ubuntu
16.04 with 2.0.7-0ubuntu1~16.04.2, which is the package patched for the
issue that I announced in this thread. I couldn't reproduce it.

I then installed an old 2.0.6 based deb (2.0.6-0ubuntu1~ubuntu16.04.1)
and still couldn't reproduce it.

I'd suggest opening an upstream bug here:

(Normally, they prefer private security bugs on Launchpad but your
report to this list is already public so I don't see a need.)


> Stiepan
> -------- Original Message --------
> Subject: [oss-security] LXC: CVE-2017-5985: lxc-user-nic didn't verify network namespace ownership
> Local Time: 9 March 2017 5:54 PM
> UTC Time: 9 March 2017 16:55
> From:
> To:
> Stéphane Graber <>
> Jann Horn discovered that the lxc-user-nic program could be tricked into
> operating on a network namespace over which the caller did not hold
> privilege.
> The behavior didn't follow what was documented in the lxc-user-nic(1)
> man page:
> It ensures that the calling user is privileged over the network
> namespace to which the interface will be attached.
> This issue is CVE-2017-5985.
> Tyler

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