Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 2.03% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-21334High confidence
environment variable leak
containerd · containerd
Official source article: GitHub GHSA-6G2Q-W5J3-FWH4 ↗. Check the applicable product and release in the original source.
6.3MediumCVSS 3.1
Scheduled
Patch availableMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs containerd containerd and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Distribution package intelligence
10 package statesRelease-specific package status
Alpine, Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Alpine v3.23v3.23 · community | containerd | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.4.4-r0 | Alpine Security Database ↗Source updated 11 Sep 2026 |
| Alpine v3.23v3.23 · community | k3s | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.20.5.1-r0 | Alpine Security Database ↗Source updated 11 Sep 2026 |
| Alpine v3.22v3.22 · community | containerd | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.4.4-r0 | Alpine Security Database ↗Source updated 11 Sep 2026 |
| Alpine v3.22v3.22 · community | k3s | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.20.5.1-r0 | Alpine Security Database ↗Source updated 11 Sep 2026 |
| Alpine v3.21v3.21 · community | containerd | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.4.4-r0 | Alpine Security Database ↗Source updated 19 Aug 2026 |
| Alpine v3.21v3.21 · community | k3s | Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected. | 1.20.5.1-r0 | Alpine Security Database ↗Source updated 19 Aug 2026 |
| Debian trixietrixie · source | containerd | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.4.4~ds1-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian bookwormbookworm · source | containerd | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.4.4~ds1-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian forkyforky · source | containerd | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.4.4~ds1-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
| Debian sidsid · source | containerd | Vendor fix publishedDebian records a fixed source-package version for this release. | 1.4.4~ds1-1 | Debian Security Tracker ↗Source updated 6 Oct 2026 |
Open-source package ranges2 source-attributed ranges
These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.
| Ecosystem and package | Affected range | First fixed version | Evidence |
|---|---|---|---|
| Gogithub.com/containerd/containerd | SEMVER: introduced 1.4.0; fixed 1.4.4 | 1.4.4 | OSV record ↗aggregator derived · 10 Sep 2026 |
| Gogithub.com/containerd/containerd | SEMVER: introduced 0; fixed 1.3.10 | 1.3.10 | OSV record ↗aggregator derived · 10 Sep 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2021-21334 · CSAF 2.0 · revision 3 · status not statedRed Hat Product Securityplugin: information leak between containers via environment variables
The vendor explicitly states that these products are not affected by this CVE.
- containerd.src as a component of Red Hat Advanced Cluster Management for Kubernetes 2
- cri-o as a component of Red Hat OpenShift Container Platform 4
- cri-o.src as a component of Red Hat OpenShift Container Platform 4
- openshift-clients as a component of Red Hat OpenShift Container Platform 4
- openshift-clients-redistributable as a component of Red Hat OpenShift Container Platform 4
- openshift-clients.src as a component of Red Hat OpenShift Container Platform 4
- openshift-hyperkube as a component of Red Hat OpenShift Container Platform 4
- openshift-kube-apiserver as a component of Red Hat OpenShift Container Platform 4
- openshift-kube-controller-manager as a component of Red Hat OpenShift Container Platform 4
- openshift-kube-scheduler as a component of Red Hat OpenShift Container Platform 4
- openshift-kubelet as a component of Red Hat OpenShift Container Platform 4
- openshift.src as a component of Red Hat OpenShift Container Platform 4
- Summary
- A flaw was found in containerd CRI plugin. Containers launched through containerd's CRI implementation that share the same image may receive incorrect environment variables, including values that are defined for other containers. The highest threat from this vulnerability is to data confidentiality.
- Remediation
- No remediation text is recorded.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available01
What, why and how
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
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.
Why
The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may obtain information outside the intended access boundary.
What
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.
Why
The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may obtain information outside the intended access boundary.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Exposure of Resource to Wrong Sphere → obtain information outside the intended access boundary
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Changed: exploitation can affect a different security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-668 ↗
CWE-668: Exposure of Resource to Wrong Sphere. The product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:NCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Action
- Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 10 Mar 2021 · Last source change 3 Aug 2024, 18:09 UTC · CWE-668 · Exposure of Resource to Wrong Sphere
CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2024-0272
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.
CVE published
Fixed release or patch reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.