CVE-2021-21334Network attack vector

Cross-container secret disclosure via shared environment slice

Published Mar 10, 2021 · Updated Aug 3, 2024

Data disclosure in containerd 1.3.9 and earlier or 1.4.0 through 1.4.3 allows remote authenticated users to read other container environment values. The CRI container-creation path appends container variables into a shared-capacity image-config environment slice, so concurrent appends can overwrite values used by another container. Exploitation requires rapid creation of multiple containers from the same image with different environment variables; exposed secrets cross container security contexts without altering data or availability.

CVSS severity6.3
Medium
EPSS probability2.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Data disclosure in containerd 1.3.9 and earlier or 1.4.0 through 1.4.3 allows remote authenticated users to read other container environment values. The CRI container-creation path appends container variables into a shared-capacity image-config environment slice, so concurrent appends can overwrite values used by another container. Exploitation requires rapid creation of multiple containers from the same image with different environment variables; exposed secrets cross container security contexts without altering data or availability.

The record

CVE
CVE-2021-21334
Published
Mar 10, 2021
Updated
Aug 3, 2024
Vendor
containerd
Product
containerd
Classifications
CWE-668, T1552.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.3.10
  2. Affected versionversion=>= 1.4.0, < 1.4.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

containerd · containerdversion=< 1.3.10; version=>= 1.4.0, < 1.4.4

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
6.3NIST NVDCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
6.3GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-668Exposure of Resource to Wrong Sphere
T1552.007Unsecured Credentials: Container API

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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