# What is CVE-2021-21334? > CVE-2021-21334 is a medium-severity flaw (CVSS 6.3) in Containerd from Linuxfoundation, published on 10 March 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 2.0%. If you run an affected version, plan in the vendor’s fix. Canonical page: https://www.precursorintelligence.com/what-is/cve-2021-21334 ## At a glance - **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle. - **Precursor Intelligence risk score:** 29 out of 100 (Low); action: Monitor. Kept up to date as the evidence changes. - **Severity:** Medium (CVSS 6.3 out of 10) - **Known to be exploited:** No, not on the list of flaws known to be exploited today - **Chance of use in the next 30 days:** 2.0% (latest exploit-likelihood forecast) - **Published:** 10 March 2021 - **Record last updated:** 7 November 2023 - **Main product:** Containerd from Linuxfoundation - **Affected products:** 2 ## What is CVE-2021-21334? In plain terms It can be attacked from anywhere on the internet with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data. ### The official description In containerd (an industry-standard container runtime) before versions 1.3.10 and 1.4.4, 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 This vulnerability has been fixed in containerd 1.3.10 and containerd 1.4.4. Users should update to these versions. ### What kind of flaw is it? - CWE-668: Exposure of Resource to Wrong Sphere ### How an attack on it works - Where an attacker can be: Anywhere on the internet - How hard it is to pull off: Hard: conditions must line up - Login needed first: An ordinary user account - Does someone have to click: No, nobody has to do anything - What an attacker gets: Can read data Severity vector: `CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N` ## Is CVE-2021-21334 being exploited? Not that we know of It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.0%. That can change at any time, which is why we keep watching. Exploit likelihood over the last 7 days: 2.0%, 2.0%, 2.0%, 2.0%, 2.0%, 2.0%, 2.0%. ### Timeline - 10 March 2021: Published - 7 November 2023: Record last updated ### How Precursor Intelligence ranks it CVE-2021-21334 scores **29 out of 100 (Low)**, with the action "Monitor". Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less: - Evidence it is being exploited: biggest factor - How severe it is: strong factor - How widely exposed it is: key context - Real threat activity around it: key context 85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it. ## Who is affected by CVE-2021-21334? The published record lists 2 products. Versions are as published: "before 1.3.10" means every version up to, but not including, 1.3.10. - [Containerd](https://www.precursorintelligence.com/product/linuxfoundation/containerd) by [Linuxfoundation](https://www.precursorintelligence.com/vendors/linuxfoundation) (Application): before 1.3.10, 1.4.0 to before 1.4.4 - [Fedora](https://www.precursorintelligence.com/product/fedoraproject/fedora) by [Fedoraproject](https://www.precursorintelligence.com/vendors/fedoraproject) (Operating system): 33, 34 ## How do I fix CVE-2021-21334? 1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list. 2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list. 3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in. 4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood. ### References - [github.com](https://github.com/containerd/containerd/commit/05f951a3781f4f2c1911b05e61c160e9c30eaa8e) (Patch, Third-party advisory) - [github.com](https://github.com/containerd/containerd/releases/tag/v1.3.10) (Release notes, Third-party advisory) - [github.com](https://github.com/containerd/containerd/releases/tag/v1.4.4) (Release notes, Third-party advisory) - [github.com](https://github.com/containerd/containerd/security/advisories/GHSA-6g2q-w5j3-fwh4) (Third-party advisory) - [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KUE2Z2ZUWBHRU36ZGBD2YSJCYB6ELPXE/) - [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QIBPKSX5IOWPM3ZPFB3JVLXWDHSZTTWT/) - [lists.fedoraproject.org](https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VTXHA5JOWQRCCUZH7ZQBEYN6KZKJEYSD/) - [security.gentoo.org](https://security.gentoo.org/glsa/202105-33) (Third-party advisory) ## Questions ### What is CVE-2021-21334? CVE-2021-21334 is a medium-severity flaw in Containerd from Linuxfoundation, published on 10 March 2021. It can be attacked from anywhere on the internet with an ordinary user account, and nobody has to click anything. If it works, the attacker can read data. ### How serious is CVE-2021-21334? It scores 6.3 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-21334 is 29 out of 100, which is Low. Its action is "Monitor". No sign of exploitation and a low forecast. Patch it in your normal update cycle. ### Is CVE-2021-21334 being exploited? It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.0%. That can change at any time, which is why we keep watching. ### Which versions does CVE-2021-21334 affect? For Containerd from Linuxfoundation: before 1.3.10, 1.4.0 to before 1.4.4. The record lists 2 products in all, each with its versions, under "Who is affected" on this page. ### How do I fix CVE-2021-21334? Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. ## Does CVE-2021-21334 affect you? Precursor Intelligence keeps checking for you: - **Tell us what you run.** Pick your software from a list, or let us work it out from your website. - **We match it to every flaw.** Over 400,000 published flaws, checked against your list. - **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it. - **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools. Start free (no card, nothing to install): https://www.precursorintelligence.com/register Book a demo: https://www.precursorintelligence.com/contact