lxc-user-nic in Linux Containers (LXC) allows local users with a lxc-usernet allocation to create network interfaces on the host and choose the name of those interfaces by leveraging lack of netns ownership check.
An issue was discovered in Linux Containers (LXC) before 2016-02-22. When executing a program via lxc-attach, the nonpriv session can escape to the parent session by using the TIOCSTI ioctl to push characters into the terminal's input buffer, allowing an attacker to escape the container.
Last updated 25 August 2025
CVE-2016-8649 was assigned to the issue that allows an attacker inside of an unprivileged container to use an inherited file descriptor, of the host's /proc, to access the rest of the host's filesystem via the openat() family of syscalls. The file descriptor is needed to write to /proc/<PID>/attr/current or /proc/<PID>/attr/exec to set the AppArmor/SELinux label of the attached process.
Upstream bug:
https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1639345
Upstream patch:
https://github.com/lxc/lxc/commit/81f466d05f2a89cb4f122ef7f593ff3f279b165c
References:
http://seclists.org/oss-sec/2016/q4/515
In LXC 2.0, many template scripts download code over cleartext HTTP, and omit a digital-signature check, before running it to bootstrap containers.