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

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Summary

CVECVE-2026-39884
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-15 04:17:37 UTC
Updated2026-04-15 17:17:04 UTC
Descriptionmcp-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.

Risk And Classification

Primary CVSS: v3.1 8.3 HIGH from [email protected]

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

Problem Types: CWE-88 | CWE-88 CWE-88: Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.3HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
3.1CNADECLARED8.3HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Flux159 Mcp-server-kubernetes affected < 3.5.0 Not specified

References

ReferenceSourceLinkTags
github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-4xqg-g... 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.5.0 [email protected] github.com
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