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Public proof of conceptFix available

CVE-2021-43816

A public proof of concept exists; no exploitation attested.

  • Published2022-01-05
  • Fixed in1.5.9
  • WeaknessCWE-281

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2022-01-0519:15CVE publishedNVD

Versions per branch

NVD · OSV
Linuxfoundation containerd
BranchAffectedFixed in
1.5≥ 1.5.1, < 1.5.91.5.9
1.5≥ 1.5.0, < 1.5.91.5.9
1.5= 1.5.0no fix published
Fedoraproject fedora
BranchAffectedFixed in
34.x= 34no fix published
35.x= 35no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • containerd
    Affected
    • = >= 1.5.0, < 1.5.9no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2022-02-15

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • containerdUbuntu:Pro:16.04:LTSall versions · no fixed version listed
  • containerdUbuntu:22.04:LTSall versions · fixed in 1.5.9-0ubuntu1
  • containerdUbuntu:20.04:LTSall versions · fixed in 1.5.9-0ubuntu1~20.04.4
  • containerdUbuntu:18.04:LTSall versions · fixed in 1.5.9-0ubuntu1~18.04.1
  • containerdDebian:14all versions · fixed in 1.5.9~ds1-1
  • containerdDebian:13all versions · fixed in 1.5.9~ds1-1
  • containerdDebian:12all versions · fixed in 1.5.9~ds1-1
  • containerdCleanStartall versions · fixed in 1.5.9-r0

11 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-43816 Red Hat Product Security17 known affected

    containerd: Unprivileged pod may bind mount any privileged regular file on disk

    multicloud-operators-channel-container as a component of Red Hat Advanced Cluster Management for Kubernetes 2 · multicloud-operators-subscription-container as a component of Red Hat Advanced Cluster Management for Kubernetes 2 · multicloud-operators-subscription-release-container as a component of Red Hat Advanced Cluster Management for Kubernetes 2 · +14 more

  • RHSA-2022:4956 Red Hat Product Security204 products fixed

    Red Hat Security Advisory: Red Hat Advanced Cluster Management 2.5 security updates, images, and bug fixes

  • RHSA-2022:0735 Red Hat Product Security221 products fixed

    Red Hat Security Advisory: Red Hat Advanced Cluster Management 2.4.2 security updates and bug fixes

Full record on NVD

Fix

  1. Update Linuxfoundation containerd to 1.5.9
  2. Vendor fix Red Hat Product Security RHSA-2022:4956 · 204 productsFor Red Hat Advanced Cluster Management for Kubernetes, see the following documentation, which will be updated shortly for this release, for important instructions on installing this release: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.5/html-…
  3. Vendor fix Red Hat Product Security RHSA-2022:0735 · 221 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.4/html-single/install/index#instal…
  4. No fix available, says the vendor Red Hat Product Security CVE-2021-43816 · 13 productsAffected
  5. No fix planned, says the vendor Red Hat Product Security CVE-2021-43816 · 4 productsWill not fix

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionpoc2025-04-22
  • CNACVSS 3.18known since 2026-10-23
  • NVDCVSS 3.19.1read 2026-10-23
  • NVDCVSS 2.06read 2026-10-23
  • CNAweakness (CWE)CWE-281known since 2026-10-23
  • NVDweakness (CWE)CWE-281read 2026-10-23
  • FIRST EPSSEPSS score1.8 %2026-11-09
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryHIGH2022-01-05

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Published
2022-01-05
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-mvff-h3cj-wj9c

Frequently asked questions

What is CVE-2021-43816?

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.

Is CVE-2021-43816 actively exploited?

A proof-of-concept exploit exists for CVE-2021-43816, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2021-43816?

CVE-2021-43816 has a CVSS v3 base score of 9.1 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H.

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