CVE-2021-21334

containerd environment variable leak

Workarounds

There are no known workarounds.

For more information

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Containers launched through containerd's CRI implementation (through Kubernetes, crictl, or any other pod/container client that uses the containerd CRI service) that share the same image may receive incorrect environment variables, including values that are defined for other containers. If the affected containers have different security contexts, this may allow sensitive information to be unintentionally shared.

If you are not using containerd’s CRI implementation (through one of the mechanisms described above), you are not vulnerable to this issue.

If you are not launching multiple containers or Kubernetes pods from the same image which have different environment variables, you are not vulnerable to this issue.

If you are not launching multiple containers or Kubernetes pods from the same image in rapid succession, you have reduced likelihood of being vulnerable to this issue

CVE-2021-21334 has a CVSS score of 6.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.4, 1.3.10); upgrading removes the vulnerable code path.

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This vulnerability has been fixed in containerd 1.3.10 and containerd 1.4.4. Users should update to these versions as soon as they are released.

1. What is CVE-2021-21334? CVE-2021-21334 is a medium-severity security vulnerability in github.com/containerd/containerd (go), affecting versions >= 1.4.0, < 1.4.4. It is fixed in 1.4.4, 1.3.10.
2. How severe is CVE-2021-21334? CVE-2021-21334 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/containerd/containerd are affected by CVE-2021-21334? github.com/containerd/containerd (go) versions >= 1.4.0, < 1.4.4 is affected.
4. Is there a fix for CVE-2021-21334? Yes. CVE-2021-21334 is fixed in 1.4.4, 1.3.10. Upgrade to this version or later.
5. Is CVE-2021-21334 exploitable, and should I be worried? Whether CVE-2021-21334 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-21334 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-21334?
   • Upgrade github.com/containerd/containerd to 1.4.4 or later
   • Upgrade github.com/containerd/containerd to 1.3.10 or later

Other vulnerabilities in github.com/containerd/containerd