dbcve.org
Mcp Server KubernetesApplication · Suyogs

CVE-2026-39884

HIGH · 8.1 CVSS v3.1 Published 2026-04-15
Fix available
A fix is available. Upgrade to 3.5.0 or later.
See remediation →
87/100
Remediation priority · High
Remotely reachable Zero-click

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
mcp-server-kubernetes is a Model Context Protocol server for Kubernetes cluster management. Versions 3.4.0 and prior contain an argument injection vulnerability in the port_forward tool in src/tools/port_forward.ts, where a kubectl command is constructed via string concatenation with user-controlled input and then naively split on spaces before being passed to spawn(). Unlike all other tools in the codebase which correctly use array-based argument passing with execFileSync(), port_forward treats every space in user-controlled fields (namespace, resourceType, resourceName, localPort, targetPort) as an argument boundary, allowing an attacker to inject arbitrary kubectl flags. This enables exposure of internal Kubernetes services to the network by injecting --address=0.0.0.0, cross-namespace targeting by injecting additional -n flags, and indirect exploitation via prompt injection against AI agents connected to the MCP server. This issue has been fixed in version 3.5.0.

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 · high confidence

The mcp-server-kubernetes port_forward tool constructs kubectl commands via string concatenation with user-controlled input (namespace, resourceType, resourceName, localPort, targetPort), then naively splits on spaces before passing to spawn(). This allows attackers to inject arbitrary kubectl flags like --address=0.0.0.0 or additional -n flags, enabling exposure of internal Kubernetes services across namespaces. Other tools in the codebase correctly use array-based execFileSync() argument passing.

MitigationUpgrade mcp-server-kubernetes to version 3.5.0 or later, which implements proper array-based argument passing instead of vulnerable string concatenation.

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
Mcp Server KubernetesApplication
Affected:< 3.5.0

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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. Identify if mcp-server-kubernetes is installed
    Run 'npm list mcp-server-kubernetes' or check your package.json dependencies for 'mcp-server-kubernetes'
    Affected if The package is listed and the version is below 3.5.0
  2. Determine installed version
    Run 'npm list mcp-server-kubernetes' and note the version number displayed
    Affected if Version is less than 3.5.0 (e.g., 3.4.0, 3.3.0, etc.)
  3. Locate the port_forward tool source code
    Find the file containing the port_forward implementation, typically in the source code under a tools or commands directory
    Affected if The code uses string concatenation to build kubectl commands rather than array-based argument passing
  4. Verify the vulnerable command construction pattern
    Inspect the port_forward code for patterns like 'kubectl' + userInput or string templates with namespace/resourceType/resourceName/localPort/targetPort variables being concatenated, then split on spaces
    Affected if The code constructs the kubectl command via string concatenation and uses .split(' ') before passing to spawn() or execFileSync()

You are affected if mcp-server-kubernetes version is below 3.5.0 AND the port_forward tool is being used, as the vulnerable string concatenation pattern allows injection of arbitrary kubectl flags.

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 3.5.0 or later
Fixed in 3.5.0
Interim mitigation

Upgrade mcp-server-kubernetes to version 3.5.0 or later, which implements proper array-based argument passing instead of vulnerable string concatenation.

Recommended fix High confidence

3.5.0

  1. 1. Identify the current installed version of mcp-server-kubernetes by checking package.json, package-lock.json, or running npm list mcp-server-kubernetes
  2. 2. If running from source, update package.json to specify version 3.5.0 or later: npm install mcp-server-kubernetes@^3.5.0
  3. 3. If using a container image, update the image tag to version 3.5.0 or later
  4. 4. Rebuild and redeploy the service
  5. 5. Verify the upgrade was successful by checking the installed version
  6. 6. Test the port_forward functionality to confirm the vulnerability is remediated

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

Fix this in Mcp Server Kubernetes Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

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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-2026-39884 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data