CVE-2026-39884 json
MCP Server Kubernetes has Argument Injection in its port_forward tool via space-splitting
published 2026-04-14 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-22807 , GHSA-4xqg-gf5c-ghwq
- cvss
- 8.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 17%
- public exploits
- 0
- none known
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.
Patch / fix
- npm mcp-server-kubernetes 3.5.0
- suyogs mcp-server-kubernetes 3.5.0
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- total
- Assessed
- 6 mo ago
Exploit prediction
0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-4xqg-gf5c-ghwq referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 8.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L |
| GitHub | 3.1 | 8.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L |
| NVD | 3.1 | 8.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | mcp-server-kubernetes | <3.5.0 |
3.5.0 |
Affected products
- Flux159 mcp-server-kubernetes
Classification
- Weakness
-
- CWE-88 Improper Neutralization of Argument Delimiters in a Command
References
-
github.com
/Flux159/mcp-server-kubernetes/security/advisories/GHSA-4xqg-gf5c-ghwq
exploit, web, mitigation, vendor-advisory
-
github.com
/Flux159/mcp-server-kubernetes/releases/tag/v3.5.0
web, product, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-39884
advisory
-
github.com
/Flux159/mcp-server-kubernetes
package
Sources
- CVE List CVE-2026-39884
- GitHub Advisory GHSA-4xqg-gf5c-ghwq
- NVD CVE-2026-39884
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.