BREW-MCP-SERVER-KUBERNETES-CVE-2026-46519

BREW-MCP-SERVER-KUBERNET… (CVE-2026-46519)

Vulnerability from osv_homebrew – Published: 2026-08-13 17:13 – Updated: 2026-09-15 09:47 – Source website

Summary

mcp-server-kubernetes Affected By Tool Access Control Bypass: Presentation-Layer Filtering Without Execution-Layer Enforcement

Details

mcp-server-kubernetes is a Model Context Protocol server for Kubernetes cluster management. Prior to version 3.6.0, mcp-server-kubernetes exposes three environment variables (ALLOW_ONLY_READONLY_TOOLS, ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS, ALLOWED_TOOLS) documented as access controls for restricting which Kubernetes operations are available. These controls are enforced at the tool discovery layer (tools/list) but not at the execution layer (tools/call). Any client that knows a tool name can invoke it directly regardless of the configured restriction mode. The access control was effectively cosmetic. This issue has been patched in version 3.6.0.

Severity

8.8 (High)


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

References

URL

Type

	https://github.com/Flux159/mcp-server-kubernetes/…	WEB
	https://github.com/CVEProject/cvelistV5/tree/main…	ADVISORY
	https://github.com/Flux159/mcp-server-kubernetes/…	ADVISORY
	https://nvd.nist.gov/vuln/detail/CVE-2026-46519	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "upstream_fixed_in": "3.6.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "mcp-server-kubernetes",
        "purl": "pkg:brew/mcp-server-kubernetes"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.1.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "git",
    "upstream_evidence": [
      {
        "ecosystem": "GIT",
        "key": "https://github.com/flux159/mcp-server-kubernetes",
        "name": "https://github.com/flux159/mcp-server-kubernetes",
        "strategy": "git",
        "subject_version": "4.1.7"
      },
      {
        "ecosystem": "npm",
        "key": "pkg:npm/mcp-server-kubernetes@4.1.7",
        "name": "mcp-server-kubernetes",
        "strategy": "registry",
        "subject_version": "4.1.7"
      }
    ]
  },
  "details": "mcp-server-kubernetes is a Model Context Protocol server for Kubernetes cluster management. Prior to version 3.6.0, mcp-server-kubernetes exposes three environment variables (ALLOW_ONLY_READONLY_TOOLS, ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS, ALLOWED_TOOLS) documented as access controls for restricting which Kubernetes operations are available. These controls are enforced at the tool discovery layer (tools/list) but not at the execution layer (tools/call). Any client that knows a tool name can invoke it directly regardless of the configured restriction mode. The access control was effectively cosmetic. This issue has been patched in version 3.6.0.",
  "id": "BREW-mcp-server-kubernetes-CVE-2026-46519",
  "modified": "2026-09-15T09:47:30Z",
  "published": "2026-08-13T17:13:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.6.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46519.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-cr22-wjx7-2w6m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46519"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "mcp-server-kubernetes Affected By Tool Access Control Bypass: Presentation-Layer Filtering Without Execution-Layer Enforcement",
  "upstream": [
    "CVE-2026-46519",
    "GHSA-cr22-wjx7-2w6m"
  ]
}

CVE-2026-46519 (GCVE-0-2026-46519)

Vulnerability from cvelistv5 – Published: 2026-06-11 18:34 – Updated: 2026-06-11 19:40

Title

mcp-server-kubernetes Affected By Tool Access Control Bypass: Presentation-Layer Filtering Without Execution-Layer Enforcement

Summary

Severity

8.8 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-11 19:39 UTC

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/Flux159/mcp-server-kubernetes/…	x_refsource_CONFIRM
https://github.com/Flux159/mcp-server-kubernetes/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
Flux159	mcp-server-kubernetes	Affected: < 3.6.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-46519",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-11T19:39:57.663035Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-11T19:40:22.771Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-cr22-wjx7-2w6m"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "mcp-server-kubernetes",
          "vendor": "Flux159",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.6.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "mcp-server-kubernetes is a Model Context Protocol server for Kubernetes cluster management. Prior to version 3.6.0, mcp-server-kubernetes exposes three environment variables (ALLOW_ONLY_READONLY_TOOLS, ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS, ALLOWED_TOOLS) documented as access controls for restricting which Kubernetes operations are available. These controls are enforced at the tool discovery layer (tools/list) but not at the execution layer (tools/call). Any client that knows a tool name can invoke it directly regardless of the configured restriction mode. The access control was effectively cosmetic. This issue has been patched in version 3.6.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-863",
              "description": "CWE-863: Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-11T18:34:15.281Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-cr22-wjx7-2w6m",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-cr22-wjx7-2w6m"
        },
        {
          "name": "https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.6.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.6.0"
        }
      ],
      "source": {
        "advisory": "GHSA-cr22-wjx7-2w6m",
        "discovery": "UNKNOWN"
      },
      "title": "mcp-server-kubernetes Affected By Tool Access Control Bypass: Presentation-Layer Filtering Without Execution-Layer Enforcement"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-46519",
    "datePublished": "2026-06-11T18:34:15.281Z",
    "dateReserved": "2026-05-14T19:12:32.755Z",
    "dateUpdated": "2026-06-11T19:40:22.771Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-CR22-WJX7-2W6M

Vulnerability from github – Published: 2026-05-21 20:33 – Updated: 2026-06-12 19:26

Summary

MCP Server Kubernetes: Tool Access Control Bypass via Presentation-Layer Filtering Without Execution-Layer Enforcement

Details

Summary

mcp-server-kubernetes exposes three environment variables (ALLOW_ONLY_READONLY_TOOLS, ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS, ALLOWED_TOOLS) documented as access controls for restricting which Kubernetes operations are available. These controls are enforced at the tool discovery layer (tools/list) but not at the execution layer (tools/call). Any client that knows a tool name can invoke it directly regardless of the configured restriction mode. The access control was effectively cosmetic.

Fixed in v3.6.0.

Impact

An attacker or misconfigured AI agent with network access to the MCP server's HTTP endpoint could invoke any Kubernetes tool regardless of the restriction mode configured by the operator -- including kubectl_delete, exec_in_pod, kubectl_generic, and node_management.

The project explicitly supports and documents multi-client HTTP deployment scenarios (Streamable HTTP and SSE transports, in-cluster deployments, Codex CLI and Gemini CLI integrations). In these deployments, operators relied on the tool restriction env vars to enforce least-privilege access across users or roles. The bypass invalidated that model entirely.

Severity scales with the Kubernetes service account's permissions. In environments where the MCP server runs with cluster-admin (common in dev/staging), this is equivalent to full cluster compromise for any client that can reach the endpoint.

The MCP_AUTH_TOKEN / X-MCP-AUTH mechanism controls who can reach the endpoint but provides no per-tool authorization. An authenticated client restricted to ALLOWED_TOOLS=kubectl_get could still invoke kubectl_delete after authentication.

Root Cause

In src/index.ts, the ListToolsRequestSchema handler applied the configured filtering logic before returning available tools. The CallToolRequestSchema handler dispatched directly by tool name with no equivalent check -- every tool was reachable unconditionally.

Proof of Concept

Tested across all three restriction modes against a live kind cluster. In each case, kubectl_delete was absent from tools/list but executed successfully via a direct tools/call request:

curl -s http://<HOST>:3003/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"kubectl_delete","arguments":{"resourceType":"pod","name":"test-pod","namespace":"default"}}}'

Result: {"result":{"content":[{"type":"text","text":"pod \"test-pod\" deleted\n"}]}}

Confirmed across ALLOW_ONLY_READONLY_TOOLS=true, ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS=true, and ALLOWED_TOOLS=kubectl_get.

Remediation

The fix applies the same filtering logic from ListToolsRequestSchema at the start of the CallToolRequestSchema handler, returning an error for any tool call outside the active allowed set. Fixed in v3.6.0.

Credit

Discovered by Francisco Rosales of Manifold Security, coordinated by Ax Sharma, Head of Research at Manifold Security.

Severity

8.8 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "mcp-server-kubernetes"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.6.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-46519"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-21T20:33:46Z",
    "nvd_published_at": "2026-06-11T19:16:42Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\n`mcp-server-kubernetes` exposes three environment variables (`ALLOW_ONLY_READONLY_TOOLS`, `ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS`, `ALLOWED_TOOLS`) documented as access controls for restricting which Kubernetes operations are available. These controls are enforced at the tool discovery layer (`tools/list`) but not at the execution layer (`tools/call`). Any client that knows a tool name can invoke it directly regardless of the configured restriction mode. The access control was effectively cosmetic.\n\nFixed in v3.6.0.\n\n## Impact\n\nAn attacker or misconfigured AI agent with network access to the MCP server\u0027s HTTP endpoint could invoke any Kubernetes tool regardless of the restriction mode configured by the operator -- including `kubectl_delete`, `exec_in_pod`, `kubectl_generic`, and `node_management`.\n\nThe project explicitly supports and documents multi-client HTTP deployment scenarios (Streamable HTTP and SSE transports, in-cluster deployments, Codex CLI and Gemini CLI integrations). In these deployments, operators relied on the tool restriction env vars to enforce least-privilege access across users or roles. The bypass invalidated that model entirely.\n\nSeverity scales with the Kubernetes service account\u0027s permissions. In environments where the MCP server runs with `cluster-admin` (common in dev/staging), this is equivalent to full cluster compromise for any client that can reach the endpoint.\n\nThe `MCP_AUTH_TOKEN` / `X-MCP-AUTH` mechanism controls who can reach the endpoint but provides no per-tool authorization. An authenticated client restricted to `ALLOWED_TOOLS=kubectl_get` could still invoke `kubectl_delete` after authentication.\n\n## Root Cause\n\nIn `src/index.ts`, the `ListToolsRequestSchema` handler applied the configured filtering logic before returning available tools. The `CallToolRequestSchema` handler dispatched directly by tool name with no equivalent check -- every tool was reachable unconditionally.\n\n## Proof of Concept\n\nTested across all three restriction modes against a live kind cluster. In each case, `kubectl_delete` was absent from `tools/list` but executed successfully via a direct `tools/call` request:\n\n```shell\ncurl -s http://\u003cHOST\u003e:3003/mcp \\\n  -H \u0027Content-Type: application/json\u0027 \\\n  -H \u0027Accept: application/json, text/event-stream\u0027 \\\n  -d \u0027{\"jsonrpc\":\"2.0\",\"id\":2,\"method\":\"tools/call\",\"params\":{\"name\":\"kubectl_delete\",\"arguments\":{\"resourceType\":\"pod\",\"name\":\"test-pod\",\"namespace\":\"default\"}}}\u0027\n```\n\nResult: `{\"result\":{\"content\":[{\"type\":\"text\",\"text\":\"pod \\\"test-pod\\\" deleted\\n\"}]}}`\n\nConfirmed across `ALLOW_ONLY_READONLY_TOOLS=true`, `ALLOW_ONLY_NON_DESTRUCTIVE_TOOLS=true`, and `ALLOWED_TOOLS=kubectl_get`.\n\n## Remediation\n\nThe fix applies the same filtering logic from `ListToolsRequestSchema` at the start of the `CallToolRequestSchema` handler, returning an error for any tool call outside the active allowed set. Fixed in v3.6.0.\n\n## Credit\n\nDiscovered by [Francisco Rosales](https://www.linkedin.com/in/francisco-rosales-celis/) of [Manifold Security](https://manifold.security), coordinated by [Ax Sharma](https://www.linkedin.com/in/axsharma/), Head of Research at Manifold Security.",
  "id": "GHSA-cr22-wjx7-2w6m",
  "modified": "2026-06-12T19:26:31Z",
  "published": "2026-05-21T20:33:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Flux159/mcp-server-kubernetes/security/advisories/GHSA-cr22-wjx7-2w6m"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46519"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Flux159/mcp-server-kubernetes"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v3.6.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "MCP Server Kubernetes: Tool Access Control Bypass via Presentation-Layer Filtering Without Execution-Layer Enforcement"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

BREW-MCP-SERVER-KUBERNET… (CVE-2026-46519)

CVE-2026-46519 (GCVE-0-2026-46519)

GHSA-CR22-WJX7-2W6M

Summary

Impact

Root Cause

Proof of Concept

Remediation

Credit

Tags

Sightings

Nomenclature

Related by attack behaviour