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CVE-2026-34742

High

CWE-1188 — Weakness Type

                    Published: Apr 2, 2026                      ·  Modified: Apr 9, 2026                      ·  Source: NVD                

CVSS v3

8.1

🔗 NVD Official

📄 Description (English)

The Go MCP SDK used Go's standard encoding/json. Prior to version 1.4.0, the Model Context Protocol (MCP) Go SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication with StreamableHTTPHandler or SSEHandler, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. This issue has been patched in version 1.4.0.

🤖 AI Executive Summary

CVE-2026-34742 is a DNS rebinding vulnerability in Go MCP SDK versions prior to 1.4.0 that affects HTTP-based servers running on localhost without authentication. An attacker can exploit this to bypass same-origin policy restrictions and invoke tools or access resources on the local MCP server. With a CVSS score of 8.1 and no exploit currently available, this poses a significant risk to organizations using vulnerable versions of the SDK, particularly those integrating MCP servers in development or production environments.

📄 Description (Arabic)

🤖 AI Intelligence Analysis Analyzed: Apr 26, 2026 11:49

🇸🇦 Saudi Arabia Impact Assessment

This vulnerability primarily impacts Saudi technology companies, software development firms, and financial institutions that utilize the Go MCP SDK for building AI-powered applications or integrations. High-risk sectors include: Banking (SAMA-regulated institutions using MCP for customer-facing AI services), Government (NCA-regulated digital transformation initiatives), Telecommunications (STC, Mobily using MCP for service automation), and Energy (ARAMCO and subsidiaries using MCP in operational technology). The risk is elevated for organizations running development environments on shared networks or those with inadequate network segmentation.

🏢 Affected Saudi Sectors

Banking and Financial Services Government and Public Administration Telecommunications Energy and Utilities Healthcare Software Development and Technology E-commerce and Retail

🎯 MITRE ATT&CK Techniques

T1190 - Exploit Public-Facing Application T1557 - Man-in-the-Middle T1557.002 - DNS Rebinding T1021.001 - Remote Services: RDP T1021.006 - Remote Services: Windows Remote Management T1550 - Use Alternate Authentication Material T1550.004 - Use Alternate Authentication Material: Web Session Cookie

⚖️ Saudi Risk Score (AI)

7.8

/ 10.0

🔧 Remediation Steps (English)

Immediate Actions:

1. Inventory all systems using Go MCP SDK and identify versions prior to 1.4.0

2. Disable or restrict HTTP-based MCP servers running on localhost without authentication

3. Implement network-level access controls to prevent external access to localhost services



Patching Guidance:

1. Upgrade Go MCP SDK to version 1.4.0 or later immediately

2. Review and test all MCP server implementations after patching

3. Verify DNS rebinding protection is enabled in the patched version



Compensating Controls (if immediate patching not possible):

1. Implement authentication on all HTTP-based MCP servers

2. Use firewall rules to restrict access to MCP servers to trusted networks only

3. Deploy reverse proxy with Host header validation

4. Implement DNS filtering to prevent rebinding attacks

5. Use HTTPS with certificate pinning instead of HTTP



Detection Rules:

1. Monitor for HTTP requests with mismatched Host headers to localhost services

2. Alert on DNS queries followed by rapid HTTP requests to 127.0.0.1 or localhost

3. Log and review all requests to MCP endpoints from external origins

4. Monitor for unusual tool invocations or resource access patterns

🔧 خطوات المعالجة (العربية)

الإجراءات الفورية:

1. حصر جميع الأنظمة التي تستخدم Go MCP SDK وتحديد الإصدارات السابقة للإصدار 1.4.0

2. تعطيل أو تقييد خوادم HTTP-based MCP التي تعمل على localhost بدون مصادقة

3. تطبيق عناصر تحكم الوصول على مستوى الشبكة لمنع الوصول الخارجي إلى خدمات localhost

إرشادات التصحيح:

1. ترقية Go MCP SDK إلى الإصدار 1.4.0 أو أحدث فوراً

2. مراجعة واختبار جميع تطبيقات خادم MCP بعد التصحيح

3. التحقق من تفعيل حماية DNS rebinding في الإصدار المصحح

عناصر التحكم البديلة (إذا لم يكن التصحيح الفوري ممكناً):

1. تطبيق المصادقة على جميع خوادم HTTP-based MCP

2. استخدام قواعد جدار الحماية لتقييد الوصول إلى خوادم MCP للشبكات الموثوقة فقط

3. نشر reverse proxy مع التحقق من Host header

4. تطبيق تصفية DNS لمنع هجمات rebinding

5. استخدام HTTPS مع certificate pinning بدلاً من HTTP

قواعد الكشف:

1. مراقبة طلبات HTTP مع عدم تطابق Host headers لخدمات localhost

2. تنبيهات على استعلامات DNS متبوعة بطلبات HTTP سريعة إلى 127.0.0.1 أو localhost

3. تسجيل ومراجعة جميع الطلبات إلى نقاط نهاية MCP من أصول خارجية

4. مراقبة أنماط استدعاء الأدوات غير العادية أو أنماط الوصول إلى الموارد

📋 Regulatory Compliance Mapping

🟢 NCA ECC 2024

ECC 2024 A.14.2.1 - Information security requirements for supplier relationships ECC 2024 A.8.3.2 - User access management and authentication ECC 2024 A.13.1.3 - Segregation of networks

🔵 SAMA CSF

SAMA CSF ID.AM-2 - Software and hardware inventory SAMA CSF PR.AC-1 - Access control policy and procedures SAMA CSF PR.DS-2 - Data security and protection

🟡 ISO 27001:2022

ISO 27001:2022 A.5.15 - Supplier relationships ISO 27001:2022 A.8.2 - Privileged access rights ISO 27001:2022 A.8.3 - Information access restriction ISO 27001:2022 A.13.1 - Network security perimeter

🟣 PCI DSS v4.0.1

PCI DSS 1.2.1 - Firewall configuration standards PCI DSS 2.2.4 - Configure system security parameters PCI DSS 6.2 - Ensure security patches are installed

🔗 References & Sources 4

🔗

https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1...

security-advisories@github.com

Patch

🔗

https://github.com/modelcontextprotocol/go-sdk/pull/760

security-advisories@github.com

Issue Tracking Patch

🔗

https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0

security-advisories@github.com

Release Notes

🔗

https://github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6

security-advisories@github.com

Vendor Advisory

📦 Affected Products / CPE 1 entries

lfprojects:mcp_go_sdk

📊 CVSS Score

8.1

/ 10.0 — High

📊 CVSS Vector

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

Attack VectorN — None / Network

Attack ComplexityL — Low / Local

Privileges RequiredN — None / Network

User InteractionR — Required

ScopeU — Unchanged

ConfidentialityH — High

IntegrityH — High

AvailabilityN — None / Network

📋 Quick Facts

Severity High

CVSS Score8.1

CWECWE-1188

EPSS0.05%

Exploit No

Patch ✓ Yes

Published 2026-04-02

Source Feed nvd

🇸🇦 Saudi Risk Score

7.8

/ 10.0 — Saudi Risk

Priority: HIGH

🏷️ Tags

patch-available CWE-1188

🏢 Vendor Advisories

🔗 https://github.com/modelcontextprotocol/go-sdk/secur...

⚡ Actions

🔗 NVD Official Page ⚡ Exploit-DB Search 🐙 GitHub PoC Search 🎯 MITRE ATT&CK 📊 CVE Details

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CVE-2026-34742

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