CVE-2021-43816 Improper Preservation of Permissions in containerd

High 8.0 Published 5 Jan 2022 Updated 22 Apr 2025

An unprivileged container can read and write privileged host files via hostPath mounts on SELinux systems, requiring an upgrade to containerd.

Exploited in the wild: Not known
Login needed: An administrator
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2021-43816?

CVE-2021-43816 is a high-severity vulnerability in Fedoraproject Fedora, published on 5 Jan 2022. An attacker needs administrator access to exploit it, with no action from the victim.

Official description

containerd is an open source container runtime. On installations using SELinux, such as EL8 (CentOS, RHEL), Fedora, or SUSE MicroOS, with containerd since v1.5.0-beta.0 as the backing container runtime interface (CRI), an unprivileged pod scheduled to the node may bind mount, via hostPath volume, any privileged, regular file on disk for complete read/write access (sans delete). Such is achieved by placing the in-container location of the hostPath volume mount at either `/etc/hosts`, `/etc/hostname`, or `/etc/resolv.conf`. These locations are being relabeled indiscriminately to match the container process-label which effectively elevates permissions for savvy containers that would not normally be able to access privileged host files. This issue has been resolved in version 1.5.9. Users are advised to upgrade as soon as possible.

Weakness: CWE-281

Which versions are affected by CVE-2021-43816?

3 open source packages ship an affected version, including github.com/containerd/containerd. It affects 2 products.

Package	Affected	Fixed in
`github.com/containerd/containerd` Go	From `1.5.0`	`1.5.9`
`github.com/containerd/containerd` Go	From `1.5.0`	`1.5.9`
`github.com/containerd/containerd` Go	From `1.5.0`	`1.5.9`

Products include Fedoraproject Fedora, Linuxfoundation Containerd.

How do I fix CVE-2021-43816?

Upgrade github.com/containerd/containerd to 1.5.9 or later.

Is CVE-2021-43816 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-43816 exists.

All Fedoraproject Fedora vulnerabilities

Sources

Also known as CLEANSTART-2025-GQ42610, DEBIAN-CVE-2021-43816, GHSA-mvff-h3cj-wj9c, GO-2022-0278, MGASA-2022-0071, UBUNTU-CVE-2021-43816.