What’s Vulnerable › Vulnerabilities

CVE-2021-43816: Improper Preservation of Permissions in containerd

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2022-01-05 · updated 2026-06-17
• Weakness: CWE-281

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.

Affected products

• Fedoraproject Fedora: 34, 35
• containerd: from 1.5.1 before 1.5.9; 1.5.0, 1.5.0-beta0, 1.5.0-beta1, 1.5.0-beta2, 1.5.0-beta3, 1.5.0-beta4 (+4) — fixed in 1.5.9

How to fix

Upgrade to a fixed version: containerd 1.5.9. Check the vendor advisory for mitigations.

References

• https://github.com/containerd/containerd/commit/a731039238c62be081eb8c31525b988415745eea
• https://github.com/containerd/containerd/issues/6194
• https://github.com/containerd/containerd/security/advisories/GHSA-mvff-h3cj-wj9c
• https://github.com/dweomer/containerd/commit/f7f08f0e34fb97392b0d382e58916d6865100299
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GD5GH7NMK5VJMA2Y5CYB5O5GTPYMWMLX/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MPDIZMI7ZPERSZE2XO265UCK5IWM7CID/
• https://github.com/containerd/containerd/commit/a731039238c62be081eb8c31525b988415745eea
• https://github.com/containerd/containerd/issues/6194
• https://github.com/containerd/containerd/security/advisories/GHSA-mvff-h3cj-wj9c
• https://github.com/dweomer/containerd/commit/f7f08f0e34fb97392b0d382e58916d6865100299
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GD5GH7NMK5VJMA2Y5CYB5O5GTPYMWMLX/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MPDIZMI7ZPERSZE2XO265UCK5IWM7CID/

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