Logo
-

Byte Open Security

(ByteOS Network)

Log In

Sign Up

ByteOS

Security
Vulnerability Details
Registries
Custom Views
Weaknesses
Attack Patterns
Filters & Tools
Vulnerability Details :

CVE-2026-9739

Summary
Assigner-Google
Assigner Org ID-14ed7db2-1595-443d-9d34-6215bf890778
Published At-27 May, 2026 | 21:38
Updated At-28 May, 2026 | 13:20
Rejected At-
Credits

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.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:Google
Assigner Org ID:14ed7db2-1595-443d-9d34-6215bf890778
Published At:27 May, 2026 | 21:38
Updated At:28 May, 2026 | 13:20
Rejected At:
▼CVE Numbering Authority (CNA)

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.

Affected Products
Vendor
Google LLCGoogle
Product
MCP Toolbox for Databases
Default Status
unaffected
Versions
Affected
  • From 0 before PR 3054 (Fix CORS bypass) (custom)
Problem Types
TypeCWE IDDescription
CWECWE-942CWE-942: Permissive Cross-domain Policy with Untrusted Domains
Type: CWE
CWE ID: CWE-942
Description: CWE-942: Permissive Cross-domain Policy with Untrusted Domains
Metrics
VersionBase scoreBase severityVector
4.09.4CRITICAL
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
Version: 4.0
Base score: 9.4
Base severity: CRITICAL
Vector:
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
Metrics Other Info
Impacts
CAPEC IDDescription
CAPEC-275CAPEC-275: DNS Rebinding
CAPEC ID: CAPEC-275
Description: CAPEC-275: DNS Rebinding
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/googleapis/mcp-toolbox/issues/3053
N/A
https://github.com/googleapis/mcp-toolbox/pull/3054
N/A
Hyperlink: https://github.com/googleapis/mcp-toolbox/issues/3053
Resource: N/A
Hyperlink: https://github.com/googleapis/mcp-toolbox/pull/3054
Resource: N/A
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:cve-coordination@google.com
Published At:27 May, 2026 | 23:16
Updated At:29 May, 2026 | 15:42

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.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary4.09.4CRITICAL
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: Secondary
Version: 4.0
Base score: 9.4
Base severity: CRITICAL
Vector:
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
CPE Matches

Weaknesses
CWE IDTypeSource
CWE-942Secondarycve-coordination@google.com
CWE ID: CWE-942
Type: Secondary
Source: cve-coordination@google.com
Evaluator Description

Evaluator Impact

Evaluator Solution

Vendor Statements

References
HyperlinkSourceResource
https://github.com/googleapis/mcp-toolbox/issues/3053cve-coordination@google.com
N/A
https://github.com/googleapis/mcp-toolbox/pull/3054cve-coordination@google.com
N/A
Hyperlink: https://github.com/googleapis/mcp-toolbox/issues/3053
Source: cve-coordination@google.com
Resource: N/A
Hyperlink: https://github.com/googleapis/mcp-toolbox/pull/3054
Source: cve-coordination@google.com
Resource: N/A

Change History

0
Information is not available yet

Similar CVEs

3Records found

CVE-2026-11624
Matching Score-8
Assigner-Google LLC
ShareView Details
Matching Score-8
Assigner-Google LLC
CVSS Score-9.4||CRITICAL
EPSS-Not Assigned
Published-13 Jun, 2026 | 08:38
Updated-13 Jun, 2026 | 10:16
Rejected-Not Available
Known To Be Used In Ransomware Campaigns?-Not Available
KEV Added-Not Available
KEV Action Due Date-Not Available

The Model Context Protocol has a security warning advising servers to validate the "Origin" header on all incoming connections to prevent DNS rebinding attacks. Prior to the v0.25.0 release, users had no way to validate the origin's host. In v0.25.0, a new "--allowed-hosts" flag was introduced alongside the existing "--allowed-origins" flag, enabling users to specify permitted hosts at server startup. Both flags default to "*", allowing users to implement strict access controls as needed without breaking existing setups. If either flag is set to "*", the server will output a startup warning about potential vulnerabilities. Documentation has also been updated to highlight these security considerations.

Action-Not Available
Vendor-Google LLC
Product-MCP Toolbox for Databases
CWE ID-CWE-346
Origin Validation Error
CVE-2026-8537
Matching Score-6
Assigner-Android (associated with Google Inc. or Open Handset Alliance)
ShareView Details
Matching Score-6
Assigner-Android (associated with Google Inc. or Open Handset Alliance)
CVSS Score-4.3||MEDIUM
EPSS-0.03% / 8.26%
||
7 Day CHG~0.00%
Published-14 May, 2026 | 19:52
Updated-19 May, 2026 | 01:30
Rejected-Not Available
Known To Be Used In Ransomware Campaigns?-Not Available
KEV Added-Not Available
KEV Action Due Date-Not Available

Insufficient policy enforcement in ViewTransitions in Google Chrome prior to 148.0.7778.168 allowed a remote attacker to leak cross-origin data via a crafted HTML page. (Chromium security severity: High)

Action-Not Available
Vendor-Google LLC
Product-chromeChrome
CWE ID-CWE-942
Permissive Cross-domain Policy with Untrusted Domains
CVE-2026-8576
Matching Score-6
Assigner-Android (associated with Google Inc. or Open Handset Alliance)
ShareView Details
Matching Score-6
Assigner-Android (associated with Google Inc. or Open Handset Alliance)
CVSS Score-4.3||MEDIUM
EPSS-0.03% / 8.26%
||
7 Day CHG~0.00%
Published-14 May, 2026 | 19:52
Updated-21 May, 2026 | 17:08
Rejected-Not Available
Known To Be Used In Ransomware Campaigns?-Not Available
KEV Added-Not Available
KEV Action Due Date-Not Available

Inappropriate implementation in CORS in Google Chrome on Linux and ChromeOS prior to 148.0.7778.168 allowed a remote attacker to leak cross-origin data via a crafted HTML page. (Chromium security severity: Medium)

Action-Not Available
Vendor-Linux Kernel Organization, IncGoogle LLC
Product-linux_kernelchrome_oschromeChrome
CWE ID-CWE-942
Permissive Cross-domain Policy with Untrusted Domains
Details not found