MediumCVE-2021-21334

    environment variable leak (CVE-2021-21334)

    Published Sources: CVE.org, OSV

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    What is affected, what to do

    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.

    Update Containerd to version 1.3.10.

    Affected
    • Containerd gte 1.4.0, < 1.4.4..*
    • Containerd lt *..1.3.10
    Fixed in
    • Containerd 1.3.10

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.3

    XIEM Effective CVSS

    Highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.3

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: CVE.org, OSV

    2.0 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 80.5

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    83.38 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.3 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.3
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    2.0 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    80.5
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-668

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: NVD (NIST), OSV (Open Source Vulnerabilities), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    containerdcontainerd
    • < 1.3.10
    • ≥ 1.4.0, < 1.4.4
    • 1.3.10
    • —
    linuxfoundationcontainerd
    • < 1.3.10
    • 1.4.0 – < 1.4.4
    • 1.3.10
    • 1.4.4
    gogithub.com/containerd/containerd
    • —
    • 1.4.0
    • —
    • —

    Fixed in hardened container images

    Vendors of hardened images ship their own builds with a fix, often ahead of the distribution. This only concerns you if you use these images.

    Fixed in hardened container images
    Fixed in
    ChainguardChainguardctop
    • 0.7.7-r13
    ChainguardChainguardctop
    • 0.7.7-r13
    ChainguardWolfictop
    • 0.7.7-r13
    ChainguardWolfictop
    • 0.7.7-r13
    CleanStartCleanStartcontainerd
    • 1.4.4-r0
    CleanStartCleanStartk3s
    • 1.20.5.1-r0

    Source: OSV.dev, licensed CC BY 4.0.

    Vendors and products

    Affected operating systems

    Affected operating systems
    Otherfedoraprojectfedora33
    Otherfedoraprojectfedora34

    Weakness classes (CWE)

    • CWE-668Exposure of Resource to Wrong Sphere

      Class

      The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.

      Entry at MITRE CWE-668

    References & sources

    • github.comcontainerd/containerd/security/advisories/GHSA-6g2q-w5j3-fwh4web, x_refsource_CONFIRM, Third-party advisory
    • NVD (NIST)vuln/detail/CVE-2021-21334advisory
    • github.comcontainerd/cri/pull/1628web
    • github.comcontainerd/cri/pull/1629web
    • github.comcontainerd/containerd/commit/05f951a3781f4f2c1911b05e61c160e9c3…web, x_refsource_MISC, Patch, Third-party advisory
    • github.comcontainerd/containerd/commit/2d9c8aa4b3f4313982c5c999af57212a1c…web
    • github.comcontainerd/containerd/commit/cbcb2f57fbe221986f96b552855eb802f6…web
    • github.comcontainerd/containerd/releases/tag/v1.3.10web, x_refsource_MISC, Release notes, Third-party advisory
    • github.comcontainerd/containerd/releases/tag/v1.4.4web, x_refsource_MISC, Release notes, Third-party advisory
    • lists.fedoraproject.orgarchives/list/package-announce@lists.fedoraproject.org/message/…web
    • lists.fedoraproject.orgarchives/list/package-announce@lists.fedoraproject.org/message/…web
    • lists.fedoraproject.orgarchives/list/package-announce@lists.fedoraproject.org/message/…web
    • security.gentoo.orgGLSA-202105-33web, Vendor advisory, x_refsource_GENTOO, Third-party advisory
    • lists.fedoraproject.orgFEDORA-2021-470fa24f5bVendor advisory, x_refsource_FEDORA
    • lists.fedoraproject.orgFEDORA-2021-10ce8fcbf1Vendor advisory, x_refsource_FEDORA
    • lists.fedoraproject.orgFEDORA-2021-f049305892Vendor advisory, x_refsource_FEDORA
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