lxc-user-nic when asked to delete a network interface will unconditionally open a user provided path. This code path may be used by an unprivileged user to check for the existence of a path which they wouldn't otherwise be able to reach. It may also be used to trigger side effects by causing a (read-only) open of special kernel files (ptmx, proc, sys). Affected releases are LXC: 2.0 versions above and including 2.0.9; 3.0 versions above and including 3.0.0, prior to 3.0.2.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-6556
• https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1783591
• https://bugzilla.suse.com/show_bug.cgi?id=988348
• https://security.gentoo.org/glsa/201808-02
• https://usn.ubuntu.com/usn/usn-3730-1
• http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00074.html
• http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00076.html
• http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00091.html
• http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00073.html