CVE-2026-34742
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.
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LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/modelcontextprotocol/go-sdkGo | < 1.4.0 | 1.4.0 |
Affected products
2Patches
Vulnerability mechanics
References
6- github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6dnvdPatchWEB
- github.com/modelcontextprotocol/go-sdk/pull/760nvdIssue TrackingPatchWEB
- github.com/advisories/GHSA-xw59-hvm2-8pj6ghsaADVISORY
- github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6nvdVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-34742ghsaADVISORY
- github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0nvdRelease NotesWEB
News mentions
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