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TI-2026-28763 Aliases CVE-2026-39884GHSA-4xqg-gf5c-ghwq

MCP Server Kubernetes has Argument Injection in its port_forward tool via space-splitting

Priority HIGH 71CWE-88Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-88.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00258 17th percentileScored 2026-11-07
Fix Fixed mcp-server-kubernetes (Flux159): 3.5.0mcp-server-kubernetes (npm): 3.5.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Flux159mcp-server-kubernetesbefore 3.5.03.5.0Patch availableCNA
—mcp-server-kubernetes (npm)before 3.5.03.5.0Patch availableGHSA-4xqg-gf5c-ghwq
  • mcp-server-kubernetes VendorFlux159 Affected before 3.5.0 Fixed in 3.5.0 Patch available CNA
  • mcp-server-kubernetes (npm) Vendor— Affected before 3.5.0 Fixed in 3.5.0 Patch available GHSA-4xqg-gf5c-ghwq

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:suyogs:mcp-server-kubernetes:*:*:*:*:*:node.js:*:*before 3.5.0VulnerableFlux159
  • cpe:2.3:a:suyogs:mcp-server-kubernetes:*:*:*:*:*:node.js:*:* Versions before 3.5.0 Vulnerable ·Flux159

Remediation

  • Fix · CNA mcp-server-kubernetes (Flux159) Fixed in 3.5.0
  • Fix · GHSA-4xqg-gf5c-ghwq mcp-server-kubernetes (npm) Fixed in 3.5.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-39884
  2. 2026-10-03 Alias added: GHSA-4xqg-gf5c-ghwq

References

Advisory 2

Other 2

  • TI-2026-44064 MCP Server Kubernetes < 3.9.0 Argument Injection via kubectl Structured Tools CVSS 4.0CRITICAL 9.3
  • TI-2025-40841 mcp-server-kubernetes potential security issue in exec_in_pod tool CVSS 3.1HIGH 8.8

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences