CVE-2026-42457Public exploitNetwork attack vector

Privilege escalation via stored template name script injection

Published May 14, 2026 · Updated May 14, 2026

Stored XSS in affected vCluster Platform 4.4–4.7 releases allows remote authenticated users to execute scripts in another user's browser. The UI renders a SpaceInstance templateRef.name value in the namespace icon hover view without neutralizing injected HTML, allowing an img onerror handler to import an external ES module. Exploitation requires namespace-create permission and a second user's hover; the script can read that user's stored access token and act with that user's privileges.

CVSS severity9.0
Critical
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in affected vCluster Platform 4.4–4.7 releases allows remote authenticated users to execute scripts in another user's browser. The UI renders a SpaceInstance templateRef.name value in the namespace icon hover view without neutralizing injected HTML, allowing an img onerror handler to import an external ES module. Exploitation requires namespace-create permission and a second user's hover; the script can read that user's stored access token and act with that user's privileges.

The record

CVE
CVE-2026-42457
Published
May 14, 2026
Updated
May 14, 2026
Vendor
vCluster Labs
Product
vCluster Platform
Classifications
CWE-79, T1539
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 14, 2026CVE publishedPublication date reported by the CVE source.
  2. May 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=< 4.4.3
  2. Affected versionversion=>=4.5.0-alpha.0 , < 4.5.5
  3. Affected versionversion=>= 4.6.0-alpha.1, < 4.6.2
  4. Affected versionversion=>= 4.7.0-alpha.0, < 4.7.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

vCluster Labs · vCluster Platformversion=< 4.4.3; version=>=4.5.0-alpha.0 , < 4.5.5; version=>= 4.6.0-alpha.1, < 4.6.2; version=>= 4.7.0-alpha.0, < 4.7.1

Published CVSS scores

9.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1539Steal Web Session Cookie

Public exploit references

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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