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NVD / CVE Program· CNA GitHub_M

CVE-2021-21334: environment variable leak

MediumCVSS 6.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 26/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.9% (FIRST EPSS); higher than 80.4% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: containerd (Alpine:v3.12) 1.4.4-r0; k3s (Alpine:v3.14) 1.20.5.1-r0; containerd (Debian:12) 1.4.4~ds1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to containerd (Alpine:v3.12) 1.4.4-r0; k3s (Alpine:v3.14) 1.20.5.1-r0; containerd (Debian:12) 1.4.4~ds1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Mar 10, 2021
Updated
Jun 16, 2026
EPSS
1.9% · 80th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
25 / 40 · 6.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 1.9%

CNA vs NVD score

NVD
6.3
CNA · GitHub_M
6.3
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-21334

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxfoundationcontainerd
fedoraprojectfedora

Using containerd? Add it to your stack and be the first to know about CVEs like this one. (Docker)

Watch new CVEs for containerd

When you'll hear from us

  • when a new CVE affecting this product is published
  • when a record in your stack enters KEV or is weaponized

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

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Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every Monday

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • containerd containerd

    • < 1.3.10, >= 1.4.0, < 1.4.4affected
Affected versions · NVD (4)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora33
  • fedoraproject fedora34
  • linuxfoundation containerdbefore 1.3.10
  • linuxfoundation containerd1.4.0 and later · before 1.4.4

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.12containerdfrom 1.4.0 · before 1.4.4-r01.4.4-r0
Alpine:v3.14k3sbefore 1.20.5.1-r01.20.5.1-r0
Debian:12containerdbefore 1.4.4~ds1-11.4.4~ds1-1
Gogithub.com/containerd/containerdfrom 1.4.0 · before 1.4.41.4.4
Gogithub.com/containerd/containerdbefore 1.3.101.3.10
openSUSE:Leap 15.2containerdbefore 1.4.4-lp152.2.6.11.4.4-lp152.2.6.1
openSUSE:Leap 15.2dockerbefore 20.10.6_ce-lp152.2.12.120.10.6_ce-lp152.2.12.1
openSUSE:Leap 15.2runcbefore 1.0.0~rc93-lp152.2.3.11.0.0~rc93-lp152.2.3.1
openSUSE:Leap 15.3containerdbefore 1.4.4-5.32.11.4.4-5.32.1
openSUSE:Leap 15.3dockerbefore 20.10.6_ce-6.49.320.10.6_ce-6.49.3
openSUSE:Leap 15.3runcbefore 1.0.0~rc93-1.14.21.0.0~rc93-1.14.2
openSUSE:Tumbleweedcontainerdbefore 1.4.8-2.21.4.8-2.2
SUSE:Linux Enterprise Module for Containers 12containerdbefore 1.4.4-16.38.11.4.4-16.38.1
SUSE:Linux Enterprise Module for Containers 12dockerbefore 20.10.6_ce-98.66.120.10.6_ce-98.66.1
SUSE:Linux Enterprise Module for Containers 12runcbefore 1.0.0~rc93-16.8.11.0.0~rc93-16.8.1
SUSE:Linux Enterprise Module for Containers 15 SP2containerdbefore 1.4.4-5.32.11.4.4-5.32.1
SUSE:Linux Enterprise Module for Containers 15 SP2dockerbefore 20.10.6_ce-6.49.320.10.6_ce-6.49.3
SUSE:Linux Enterprise Module for Containers 15 SP2runcbefore 1.0.0~rc93-1.14.21.0.0~rc93-1.14.2

Same product

linuxfoundation: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-23648Insecure handling of image volumes in containerd CRI plugin
    38Monitor
  • CVE-2026-53488containerd CRI plugin: — image-config `LABEL` flows to restart-monitor `binary://` logger: host-root command execution from an image pull
    37Monitor
  • CVE-2021-43816Improper Preservation of Permissions in containerd
    37Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2020-15157Oct 16, 2020 · containerd can be coerced into leaking credentials during image pull
    25Monitor
  • ← EarlierCVE-2020-15257Nov 30, 2020 · containerd-shim API Exposed to Host Network Containers
    21Monitor
  • Later →CVE-2021-32760Jul 19, 2021 · Archive package allows chmod of file outside of unpack target directory
    25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:containerd1.4.4-r0 · Alpine:v3.12Package registry (OSV)
alpine:k3s1.20.5.1-r0 · Alpine:v3.14Package registry (OSV)
debian:containerd1.4.4~ds1-1 · Debian:12Package registry (OSV)
Go:github.com/containerd/containerd1.3.10Package registry (OSV)
Go:github.com/containerd/containerd1.4.4Package registry (OSV)
opensuse:containerd1.4.4-lp152.2.6.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:docker20.10.6_ce-lp152.2.12.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:runc1.0.0~rc93-lp152.2.3.1 · openSUSE:Leap 15.2Package registry (OSV)
suse:containerd1.4.4-16.38.1 · SUSE:Linux Enterprise Module for Containers 12Package registry (OSV)
suse:docker20.10.6_ce-98.66.1 · SUSE:Linux Enterprise Module for Containers 12Package registry (OSV)
suse:runc1.0.0~rc93-16.8.1 · SUSE:Linux Enterprise Module for Containers 12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-668 · Exposure of Resource to Wrong Sphere

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records