CVE-2021-21303

Terminal display manipulation via unsanitized metadata

Published Feb 5, 2021 · Updated Aug 3, 2024

Output injection in Helm 3.0 through 3.5.1 allows local users to manipulate terminal displays through crafted chart or plugin metadata. The chart version parser passes invalid SemVer strings through unchanged, while repository index, plugin.yaml, and Chart.yaml fields reach output without printable-character sanitization. Execution requires a user to run Helm against untrusted metadata; injected terminal control sequences can obscure information, alter displayed text, or clear the screen.

CVSS severity5.9
Medium
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Output injection in Helm 3.0 through 3.5.1 allows local users to manipulate terminal displays through crafted chart or plugin metadata. The chart version parser passes invalid SemVer strings through unchanged, while repository index, plugin.yaml, and Chart.yaml fields reach output without printable-character sanitization. Execution requires a user to run Helm against untrusted metadata; injected terminal control sequences can obscure information, alter displayed text, or clear the screen.

The record

CVE
CVE-2021-21303
Published
Feb 5, 2021
Updated
Aug 3, 2024
Vendor
The Helm Project
Product
Helm
Classifications
CWE-74, T1204.002
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 5, 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=> 3.0, < 3.5.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Helm Project · Helmversion=> 3.0, < 3.5.2

Published CVSS scores

5.9GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
6.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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