Vulnerability-Lookup

GHSA-7PF3-8XX7-RVHF

Vulnerability from github – Published: 2026-05-28 00:30 – Updated: 2026-05-28 00:30

Details

Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented allowed-origins and allowed-hosts flags to align with MCP security guidelines. However, the hardcoded Access-Control-Allow-Origin: * header in the SSE initialization handler was inadvertently retained. This vulnerability specifically impacts users connecting via Toolbox using SSE under specification v2024-11-05.

Severity

9.4 (Critical)


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

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JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-9739"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-942"
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    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-27T23:16:48Z",
    "severity": "CRITICAL"
  },
  "details": "Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented `allowed-origins` and `allowed-hosts` flags to align with MCP security guidelines. However, the hardcoded `Access-Control-Allow-Origin: *` header in the SSE initialization handler was inadvertently retained. This vulnerability specifically impacts users connecting via Toolbox using SSE under specification v2024-11-05.",
  "id": "GHSA-7pf3-8xx7-rvhf",
  "modified": "2026-05-28T00:30:30Z",
  "published": "2026-05-28T00:30:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9739"
    },
    {
      "type": "WEB",
      "url": "https://github.com/googleapis/mcp-toolbox/issues/3053"
    },
    {
      "type": "WEB",
      "url": "https://github.com/googleapis/mcp-toolbox/pull/3054"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
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      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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"
    }
  ]
}

CVE-2026-9739 (GCVE-0-2026-9739)

Vulnerability from cvelistv5 – Published: 2026-05-27 21:38 – Updated: 2026-05-28 13:20

Summary

Vulnerable to DNS rebinding attacks when using SSE (http://b/499408790). During the beta phase, we implemented `allowed-origins` and `allowed-hosts` flags to align with MCP security guidelines. However, the hardcoded `Access-Control-Allow-Origin: *` header in the SSE initialization handler was inadvertently retained. This vulnerability specifically impacts users connecting via Toolbox using SSE under specification v2024-11-05.

Severity

9.4 (Critical)


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

CWE

CWE-942 - Permissive Cross-domain Policy with Untrusted Domains

Assigner

Google

References

2 references

URL	Tags
https://github.com/googleapis/mcp-toolbox/issues/3053
https://github.com/googleapis/mcp-toolbox/pull/3054

Impacted products

1 product

Vendor	Product	Version
Google	MCP Toolbox for Databases	Affected: 0 , < PR 3054 (Fix CORS bypass) (custom)

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JSON

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                "id": "CVE-2026-9739",
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                "role": "CISA Coordinator",
                "timestamp": "2026-05-28T13:19:37.204820Z",
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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.

Action not permitted

GHSA-7PF3-8XX7-RVHF

CVE-2026-9739 (GCVE-0-2026-9739)

Tags

Sightings

Nomenclature