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Fencer Intel
medium 5.9

CVE-2021-21303 json

Injection attack in Helm

published 5y ago modified 2mo ago also BIT-helm-2021-21303 , EUVD-2021-1306 , GHSA-c38g-469g-cmgx , GO-2022-1040

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits
0
none known

Summary

Helm is open-source software which is essentially "The Kubernetes Package Manager". Helm is a tool for managing Charts. Charts are packages of pre-configured Kubernetes resources. In Helm from version 3.0 and before version 3.5.2, there a few cases where data loaded from potentially untrusted sources was not properly sanitized. When a SemVer in the `version` field of a chart is invalid, in some cases Helm allows the string to be used "as is" without sanitizing. Helm fails to properly sanitized some fields present on Helm repository `index.yaml` files. Helm does not properly sanitized some fields in the `plugin.yaml` file for plugins In some cases, Helm does not properly sanitize the fields in the `Chart.yaml` file. By exploiting these attack vectors, core maintainers were able to send deceptive information to a terminal screen running the `helm` command, as well as obscure or alter information on the screen. In some cases, we could send codes that terminals used to execute higher-order logic, like clearing a terminal screen. Further, during evaluation, the Helm maintainers discovered a few other fields that were not properly sanitized when read out of repository index files. This fix remedies all such cases, and once again enforces SemVer2 policies on version fields. All users of the Helm 3 should upgrade to the fixed version 3.5.2 or later. Those who use Helm as a library should verify that they either sanitize this data on their own, or use the proper Helm API calls to sanitize the data.

Patch / fix

  • go helm.sh/helm/v3 3.5.2
  • bitnami helm 3.5.2
  • helm helm 3.5.2
  • helm Alpine 3.24, Alpine 3.23, Alpine 3.22 +5 more 3.6.0-r0

alpine advisories ALPINE-CVE-2021-21303

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • helm CBL-Mariner 2.0 3.4.1-4

azure linux advisories AZL-6470

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • helm Arch Linux 3.5.2-1

arch linux advisories AVG-1539

Is CVE-2021-21303 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21303 updated cvss 6.8

helm: Unsanitized data displayed directly to user's terminal

  • Red Hat Advanced Cluster Management for Kubernetes 2 multicloudhub-repo, multicloud-operators-subscription, multicloud-operators-subscription-release Red Hat OpenStack Platform 16.2 osp-director-provisioner-container, rhosp-rhel8-tech-preview/osp-director-operator, rhosp-rhel8-tech-preview/osp-director-downloader
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.09% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
NVD 3.1 6.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
NVD 2.0 3.5 AV:N/AC:M/Au:S/C:N/I:P/A:N
OSV 3.1 6.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
go helm.sh/helm/v3
>=3.0.0, <3.5.2
3.5.2
bitnami helm
>=3.0.0, <3.5.2
3.5.2

Affected products

  • helm helm

Classification

Weakness
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component

References

Sources

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