Tõnis Tiigi

A time-of-check to time-of-use (TOCTOU) vulnerability was found in containerd. This issue allows specially crafted container images to arbitrarily modify the host file system while unpacking an image during an image pull.

The docker packages version docker-1.13.1-108.git4ef4b30.el7 as released for Red Hat Enterprise Linux 7 Extras via RHBA-2020:0053 (https://access.redhat.com/errata/RHBA-2020:0053) included an incorrect version of runc that was missing multiple bug and security fixes. One of the fixes regressed in that update was the fix for CVE-2016-9962, that was previously corrected in the docker packages in Red Hat Enterprise Linux 7 Extras via RHSA-2017:0116 (https://access.redhat.com/errata/RHSA-2017:0116). The CVE-2020-14300 was assigned to this security regression and it is specific to the docker packages produced by Red Hat. The original issue - CVE-2016-9962 - could possibly allow a process inside container to compromise a process entering container namespace and execute arbitrary code outside of the container. This could lead to compromise of the container host or other containers running on the same container host. This issue only affects a single version of Docker, 1.13.1-108.git4ef4b30, shipped in Red Hat Enterprise Linux 7. Both earlier and later versions are not affected.

The issue is related to a flaw in tracking additional container processes using the container's pid 1, which can be exploited to gain access to sensitive data, compromise data integrity, and cause a denial of service. Specifically, the vulnerability allows the main processes of the container, if running as root, to gain access to file-descriptors of new processes during initialization, potentially leading to container escapes or modification of the runC state before the process is fully placed inside the container.

The issue allows local users to gain privileges via a symlink attack in an image. This occurs because Libcontainer and Docker Engine open the file-descriptor passed to the pid-1 process before performing the chroot.

The issue allows local users to escape containerization and write to arbitrary files on the host system via a symlink attack in an image when respawning a container. This is due to a "mount namespace breakout" in Libcontainer.