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Azure HdinsightApplication · Microsoft

CVE-2026-21529

MEDIUM · 5.4 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 5.1 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper neutralization of input during web page generation ('cross-site scripting') in Azure HDInsights allows an authorized attacker to perform spoofing over a network.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a cross-site scripting (XSS) vulnerability in Azure HDInsights where improper input neutralization during web page generation allows an authorized attacker to inject malicious scripts into web pages viewed by other users, enabling session hijacking and spoofing attacks.

MitigationImplement proper input validation, context-aware output encoding, and Content Security Policy (CSP) headers to prevent script injection. Review and sanitize all user-supplied input before reflecting it in web pages.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Azure HdinsightApplication
Affected:< 5.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Azure HDInsight cluster version
    Run 'az hdinsight show --resource-group <rg-name> --name <cluster-name> --query "properties.clusterVersion"' or view the cluster properties in Azure Portal under the Overview blade
    Affected if The cluster version is below 5.1 (e.g., 4.0, 5.0.x)
  2. Verify Ambari web UI is accessible
    Check if port 8080 or 8443 is open on the cluster head nodes. Use 'az network nsg rule list' or check the NSG configuration for inbound rules allowing HTTP/HTTPS to these ports
    Affected if The Ambari web interface is exposed externally via public IP without proper network isolation
  3. Identify exposed web endpoints
    Review the cluster's Apache Ambari, Apache Zeppelin, or other web-based service configurations. Check which endpoints are bound to 0.0.0.0 versus localhost only
    Affected if Web services are bound to all interfaces (0.0.0.0) and accessible from outside the cluster
  4. Inspect HTTP response headers for CSP
    Capture an HTTP response from Ambari or Zeppelin web UI (e.g., using browser DevTools or curl) and check for Content-Security-Policy headers
    Affected if No CSP headers are present or they are insufficiently restrictive, allowing inline scripts

The environment is affected if the Azure HDInsight cluster version is below 5.1 AND the Ambari or other web UIs are exposed, as the XSS flaw requires both the vulnerable version AND accessible web interfaces to be exploited.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.1 or later
Fixed in 5.1
Interim mitigation

Implement proper input validation, context-aware output encoding, and Content Security Policy (CSP) headers to prevent script injection. Review and sanitize all user-supplied input before reflecting it in web pages.

Recommended fix Moderate confidence

Azure HDInsight version 5.1 or later

  1. 1. Identify current Azure HDInsight cluster version by checking the cluster properties in Azure Portal or using Azure CLI: `az hdinsight show --resource-group <rg-name> --name <cluster-name>`
  2. 2. If the cluster version is below 5.1, plan an upgrade following Azure HDInsight upgrade documentation
  3. 3. Before upgrading production clusters, test the upgrade in a staging environment to validate compatibility
  4. 4. Create a backup of cluster configurations and data as a precautionary measure
  5. 5. Execute the upgrade through Azure Portal or Azure CLI: `az hdinsight upgrade --resource-group <rg-name> --name <cluster-name> --target-version 5.1` or appropriate upgrade method
  6. 6. After upgrade, verify cluster health and validate that all workloads function correctly
  7. 7. Review cluster dashboards and logs to confirm the XSS vulnerability has been addressed
Caveat Review Azure HDInsight 5.1 release notes for any breaking changes or deprecated features before upgrading production clusters

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Azure Hdinsight Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
36.0 hours of engineering $6,400
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-21529 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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