CVE-2021-43816
Unprivileged pod using `hostPath` can side-step active LSM when it is SELinux in github.com/containerd/containerd
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.
How to fix CVE-2021-43816
To remediate CVE-2021-43816, upgrade the affected package to a fixed version below.
- —upgrade to 1.5.9~ds1-1 or later
- —upgrade to 1.5.9 or later
- —upgrade to 1.5.9 or later
Is CVE-2021-43816 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 1.5.9~ds1-1
- >= 1.5.0, < 1.5.9
- >= 1.5.0, < 1.5.9
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH8.0 | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H |