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

> Attackers can inject arbitrary kubectl flags via space-splitting in the port_forward tool, enabling network exposure or cross-namespace access.

- **Severity:** High 8.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Apr 2026
- **Updated:** 15 Apr 2026
- **Also known as:** GHSA-4xqg-gf5c-ghwq

## What is CVE-2026-39884?

CVE-2026-39884 is a high-severity command injection vulnerability in Flux159 mcp-server-kubernetes, published on 14 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-88 (Improper Neutralization of Argument Delimiters in a Command)

## Which versions are affected by CVE-2026-39884?

2 open source packages ship an affected version, including mcp-server-kubernetes. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mcp-server-kubernetes` | npm | All versions | 3.5.0 |
| `mcp-server-kubernetes` | npm | All versions | 3.5.0 |

Products: Suyogs Mcp-Server-Kubernetes.

## How do I fix CVE-2026-39884?

Upgrade mcp-server-kubernetes to 3.5.0 or later.

## Is CVE-2026-39884 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39884 exists.

## Other vulnerabilities in Flux159 mcp-server-kubernetes

- [CVE-2026-61459](https://insights.sbomify.com/CVE-2026-61459/): MCP Server Kubernetes < 3.9.0 Argument Injection via kubectl Structured Tools (critical 9.3)
- [CVE-2025-66404](https://insights.sbomify.com/CVE-2025-66404/): mcp-server-kubernetes potential security issue in exec_in_pod tool (medium 6.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39884 and fix it if it is affected.

What it is: CVE-2026-39884 is a high-severity command injection vulnerability in Flux159 mcp-server-kubernetes, published on 14 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39884 exists.

Affected packages and fixed versions:
- mcp-server-kubernetes (npm): affected all versions; fixed in 3.5.0
- mcp-server-kubernetes (npm): affected all versions; fixed in 3.5.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39884/ (Markdown: https://insights.sbomify.com/CVE-2026-39884/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39884
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39884
- OSV: https://osv.dev/vulnerability/CVE-2026-39884

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39884/
Summaries are generated and may contain mistakes; the official description above is the record.