Vulnerability-Lookup

CVE-2026-81094 (GCVE-0-2026-81094)

Vulnerability from cvelistv5 – Published: 2026-08-27 14:50 – Updated: 2026-08-27 18:01

Title

mcp-router CLI before 0.6.3 Binds the MCP Aggregator to All Interfaces Without Requiring Authentication

Summary

The mcp-router CLI served its MCP aggregator on every interface and enforced authentication only when the operator asked for it. The serve command in apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed port, and required a token only when the corresponding flag was supplied, so a default invocation exposed the aggregator, and every MCP server it fronted, to anyone able to reach the port. Release 0.6.3 defaults the host to the loopback address and refuses to start without a token whenever the host it is given is not a loopback address; no earlier release carries either check.

Severity

9.3 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

9.1 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-27 18:01 UTC

CWE

CWE-306 - Missing Authentication for Critical Function

Assigner

VulnCheck mitre root

References

5 references

URL	Tags
https://github.com/mcp-router/mcp-router	product
https://github.com/mcp-router/mcp-router/security…	vendor-advisory
https://github.com/mcp-router/mcp-router/commit/4…	patch
https://github.com/mcp-router/mcp-router/blob/v0.…	technical-description
https://www.vulncheck.com/advisories/mcp-router-c…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
mcp-router	mcp-router	Affected: 0 , < 0.6.3 (semver) Unaffected: 4c4642cfd274097ec8b33ecd3047390829c79d35 (git)	guessed

Date Public

2026-08-26 00:00

Credits

Yotam Perkal (Pluto Security)

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-81094

Vulnerability from fkie_nvd - Published: 2026-08-27 17:20 - Updated: 2026-08-27 20:18

Severity

9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Summary

References

	URL	Tags
	disclosure@vulncheck.com	https://github.com/mcp-router/mcp-router
	disclosure@vulncheck.com	https://github.com/mcp-router/mcp-router/blob/v0.6.3/apps/cli/src/commands/serve.ts#L105
	disclosure@vulncheck.com	https://github.com/mcp-router/mcp-router/commit/4c4642cfd274097ec8b33ecd3047390829c79d35
	disclosure@vulncheck.com	https://github.com/mcp-router/mcp-router/security/advisories/GHSA-rx55-5c7h-r56r
	disclosure@vulncheck.com	https://www.vulncheck.com/advisories/mcp-router-cli-before-0.6.3-binds-the-mcp-aggregator-to-all-interfaces-without-requiring-authentication

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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  "lastModified": "2026-08-27T20:18:49.427",
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          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
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          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-81094",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-27T18:01:21.151738Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-27T17:20:51.650",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/mcp-router/mcp-router"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/mcp-router/mcp-router/blob/v0.6.3/apps/cli/src/commands/serve.ts#L105"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/mcp-router/mcp-router/commit/4c4642cfd274097ec8b33ecd3047390829c79d35"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/mcp-router/mcp-router/security/advisories/GHSA-rx55-5c7h-r56r"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/mcp-router-cli-before-0.6.3-binds-the-mcp-aggregator-to-all-interfaces-without-requiring-authentication"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-306"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

GHSA-G448-X63H-M2M3

Vulnerability from github – Published: 2026-08-27 18:32 – Updated: 2026-08-27 18:32

Details

Severity

9.1 (Critical)


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

9.3 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-81094"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-27T17:20:51Z",
    "severity": "CRITICAL"
  },
  "details": "The mcp-router CLI served its MCP aggregator on every interface and enforced authentication only when the operator asked for it. The serve command in apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed port, and required a token only when the corresponding flag was supplied, so a default invocation exposed the aggregator, and every MCP server it fronted, to anyone able to reach the port. Release 0.6.3 defaults the host to the loopback address and refuses to start without a token whenever the host it is given is not a loopback address; no earlier release carries either check.",
  "id": "GHSA-g448-x63h-m2m3",
  "modified": "2026-08-27T18:32:25Z",
  "published": "2026-08-27T18:32:25Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mcp-router/mcp-router/security/advisories/GHSA-rx55-5c7h-r56r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81094"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mcp-router/mcp-router/commit/4c4642cfd274097ec8b33ecd3047390829c79d35"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mcp-router/mcp-router"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mcp-router/mcp-router/blob/v0.6.3/apps/cli/src/commands/serve.ts#L105"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/mcp-router-cli-before-0.6.3-binds-the-mcp-aggregator-to-all-interfaces-without-requiring-authentication"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

CVE-2026-81094 (GCVE-0-2026-81094)

FKIE_CVE-2026-81094

GHSA-G448-X63H-M2M3

Tags

Sightings

Nomenclature