Bug 2454608 (CVE-2026-34742) - CVE-2026-34742 github.com/modelcontextprotocol/go-sdk: Model Context Protocol (MCP) Go SDK: DNS rebinding vulnerability allows unauthorized access
Summary: CVE-2026-34742 github.com/modelcontextprotocol/go-sdk: Model Context Protocol...
Keywords:
Status: NEW
Alias: CVE-2026-34742
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2454683 2454684
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-02 19:07 UTC by OSIDB Bzimport
Modified: 2026-04-02 22:23 UTC (History)
26 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-04-02 19:07:03 UTC 
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.
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