CVE-2026-34742
Lfprojects Mcp Go Sdk ≤ 1.4.0
Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/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:XSummary
CVE-2026-34742 is a high-severity Initialization of a Resource with an Insecure Default (CWE-1188) vulnerability in Lfprojects Mcp Go Sdk. Its CVSS base score is 7.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Default Accounts (T1078.001); ranked at the 37th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the Protocol-Specific Risks risk domain.
The strongest mitigations our analysis identified map to CM-2 (Baseline Configuration) and CM-6 (Configuration Settings) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-34742 affects the Model Context Protocol (MCP) Go SDK in versions prior to 1.4.0. The vulnerability arises because the SDK does not enable DNS rebinding protection by default for HTTP-based servers, specifically when using StreamableHTTPHandler or SSEHandler on localhost without authentication. This flaw, tied to CWE-1188, allows potential bypass of browser same-origin policy restrictions and has a CVSS v3.1 base score of 8.1 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N).
A remote attacker can exploit this issue by luring a user to visit a malicious website. The site leverages DNS rebinding to send requests to the victim's local MCP server, bypassing same-origin policy protections. Successful exploitation enables the attacker to invoke tools or access resources exposed by the MCP server on the user's behalf, resulting in high confidentiality and integrity impacts under the specified conditions.
The issue has been patched in MCP Go SDK version 1.4.0. Mitigation involves upgrading to this version or later. Relevant details are provided in the project's GitHub security advisory (GHSA-xw59-hvm2-8pj6), the patching commit (67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d), pull request #760, and release notes for v1.4.0.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18503
Vulnerability Data
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…
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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.
- CWE(s)
AI Security AnalysisAI
- AI Category
- AI Agent Protocols and Integrations
- Risk Domain
- Protocol-Specific Risks
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: mcp, model context protocol
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 13 hardening rules · 7 OS baselines
V14.3.2V6.3.2V11.3.1V13.2.3
Mitigating Controls (NIST 800-53 r5) AI
Baseline configuration directly requires documenting and maintaining secure initial settings instead of insecure defaults.
Configuration settings mandate the most restrictive values be applied at initialization, eliminating reliance on insecure factory defaults.
Least privilege reduces the blast radius of any insecure default permissions that remain after initialization.
Security engineering principles include explicit requirements for secure defaults during resource initialization and design.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Hardened baselines and configuration management directly replace insecure defaults with secure settings.
Secure development practices include designing products with secure defaults rather than insecure ones.
Pre-acquisition integrity checks can reject products known to ship with insecure defaults.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Mandating secure baseline templates and immediate replacement of vendor defaults directly stops systems from being deployed with insecure factory settings that attackers can exploit.
Requiring documented specification, testing, and acceptance of changes ensures that new or modified components are not initialized with insecure default settings that would otherwise be left in production.
Requiring suppliers to document secure configuration and implemented security functions reduces the likelihood that products will be initialised with insecure default settings.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248823 OL 8 must not have the telnet-server package installed. prevents CWE-1188
RHEL 7 (1 rule)
- V-204627 SNMP community strings on the Red Hat Enterprise Linux operating system must be changed from the default. prevents CWE-1188
Ubuntu 22.04 (1 rule)
- V-260529 Ubuntu 22.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Ubuntu 24.04 (1 rule)
- V-270708 Ubuntu 24.04 LTS must be configured so that remote X connections are disabled, unless to fulfill documented and validated mission requirements. prevents CWE-1188
Windows Server 2016 (1 rule)
- V-224972 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188
Windows Server 2019 (1 rule)
- V-205741 Windows Server 2019 Active Directory Group Policy objects must have proper access control permissions. prevents CWE-1188