The lxc-sshd template (templates/lxc-sshd.in) in LXC before 1.0.0.beta2 uses read-write permissions when mounting /sbin/init, which allows local users to gain privileges by modifying the init file.

Brief introduction 

CVE-2013-6441

The template script lxc-sshd used to mount itself as /sbin/init in the container using a writable bind-mount.

This update resolved the above issue by using a read-only bind-mount instead preventing any form of potentially accidental damage.

CVE-2015-1335

On container startup, lxc sets up the container's initial file system tree by doing a bunch of mounting, guided by the container's configuration file.

The container config is owned by the admin or user on the host, so we do not try to guard against bad entries.
However, since the mount target is in the container, it's possible that the container admin could divert the mount with symbolic links. This could bypass proper container startup (i.e. confinement of a root-owned container by the restrictive apparmor policy, by diverting the required write to /proc/self/attr/current), or bypass the (path-based) apparmor policy by diverting, say, /proc to /mnt in the container.

This update implements a safe_mount() function that prevents lxc from doing mounts onto symbolic links.

NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The container framework LXC has been updated to fix various bugs and a security issue :

  - The sshd template allowed privilege escalation on the     host. (CVE-2013-6441)

  - SLES container time not aligned with host time.
    (bnc#839653)

  - SLES container boot takes ages. (bnc#839663)

  - lxc mounts /dev/pts with wrong options (bnc#869663)

Florian Sagar discovered that the LXC sshd template set incorrect mount permissions. An attacker could possibly use this flaw to cause privilege escalation on the host.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
89042	Debian DLA-442-1 : lxc security update	Nessus	Debian Local Security Checks	high
74021	SuSE 11.3 Security Update : lxc (SAT Patch Number 9084)	Nessus	SuSE Local Security Checks	high
72479	Ubuntu 13.10 : lxc vulnerability (USN-2104-1)	Nessus	Ubuntu Local Security Checks	high

Detections

Analytics

CVE-2013-6441

high

Tenable Plugins

high

high

high