CVE-2021-21334 | environment variable leak

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: 2021-03-10 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-21334 is rated Moderate Risk (54.3/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.04%). EPSS rose +1.64% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-21334

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.40% 2.04% +1.64%
2 2026-06-01 0.47% 0.40% -0.07%
3 2026-02-26 — 0.47% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-21334

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 1.8 4.0 [email protected]
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 1.8 4.0 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-21334

GitHub Security Advisory for CVE-2021-21334

GHSA-6g2q-w5j3-fwh4 · Severity: medium · Ecosystem: go — containerd environment variable leak

OS Trackers for CVE-2021-21334

vendor priority summary link
alpine medium CVE-2021-21334: 2 source package rows (containerd, k3s); 26 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 14, open 12. https://security.alpinelinux.org/vuln/CVE-2021-21334
debian not yet assigned CVE-2021-21334 not yet assigned priority: Debian including 1 source packages (containerd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-21334
gentoo high CVE-2021-21334: 1 GLSA(s) (202105-33), 1 atom(s) (app-emulation/containerd); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-21334
redhat medium — https://access.redhat.com/security/cve/CVE-2021-21334
suse medium CVE-2021-21334 severity moderate: SUSE including 273 source package names (2.0.2-4.2.20:runc-1.0.0~rc93-1.14.2, amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, …), 1251 product×package rows across 326 product lines (Container rancher/elemental-teal-iso/5.4, Container rancher/elemental-teal-rt/5.4, … (326 product lines)): Fixed 1062, Known Affected 136, Known Not Affected 53. https://www.suse.com/security/cve/CVE-2021-21334/
ubuntu medium CVE-2021-21334 medium priority: Ubuntu including 1 source packages (containerd), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): released 14, DNE 1, needed 1. https://ubuntu.com/security/CVE-2021-21334

Affected software / configurations for CVE-2021-21334

Vendor Product Version Raw CPE
linuxfoundation containerd < 1.3.10 cpe:2.3:a:linuxfoundation:containerd:*:*:*:*:*:*:*:*
linuxfoundation containerd >= 1.4.0, < 1.4.4 cpe:2.3:a:linuxfoundation:containerd:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

References for CVE-2021-21334

URL Tags
https://github.com/containerd/containerd/commit/05f951a3781f4f2c1911b05e61c160e9c30eaa8e Patch Third Party Advisory
https://github.com/containerd/containerd/releases/tag/v1.3.10 Release Notes Third Party Advisory
https://github.com/containerd/containerd/releases/tag/v1.4.4 Release Notes Third Party Advisory
https://github.com/containerd/containerd/security/advisories/GHSA-6g2q-w5j3-fwh4 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KUE2Z2ZUWBHRU36ZGBD2YSJCYB6ELPXE/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QIBPKSX5IOWPM3ZPFB3JVLXWDHSZTTWT/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VTXHA5JOWQRCCUZH7ZQBEYN6KZKJEYSD/
https://security.gentoo.org/glsa/202105-33 Third Party Advisory
cvelogic Threat Intelligence