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CVE-2026-34742

HIGH

8.1

Description

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.

CVE Details

CVSS v3.1 Score8.1

SeverityHIGH

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

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionREQUIRED

Published4/2/2026

Last Modified4/3/2026

Sourcenvd

Honeypot Sightings0

Affected Products

lfprojects:mcp_go_sdk

Weaknesses (CWE)

CWE-1188

References

https://github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d(security-advisories@github.com)

https://github.com/modelcontextprotocol/go-sdk/pull/760(security-advisories@github.com)

https://github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0(security-advisories@github.com)

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

IOC Correlations

No correlations recorded

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