CVEs / CVE-2026-34742
CVE-2026-34742
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.
Affected products · 1
| Product | Versions affected | Fixed in |
|---|---|---|
| lfprojects: mcp go sdk | < 1.4.0 | 1.4.0 |
Versions as NVD's CPE configuration states them; "—" means the record gives no fixed version, not that none exists. Check the vendor's advisory in the references.
In this registry
- python-sdk — agent dossier
- typescript-sdk — agent dossier
References · 8
- github.com/modelcontextprotocol/go-sdk/commit/67bd3f2e2b53ce11a16db8d976cdb8ff1e986b6d — Patch
- github.com/modelcontextprotocol/go-sdk/pull/760 — Issue Tracking, Patch
- github.com/modelcontextprotocol/go-sdk/releases/tag/v1.4.0 — Release Notes
- github.com/modelcontextprotocol/go-sdk/security/advisories/GHSA-xw59-hvm2-8pj6 — Vendor Advisory
- access.redhat.com/errata/RHSA-2026:21772
- access.redhat.com/security/cve/CVE-2026-34742
- bugzilla.redhat.com/show_bug.cgi?id=2454608
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34742.json
The official record's references, as NVD lists them, minus any tagged Exploit. Nothing here is an exploit or a proof of concept.
Description, scores, versions and references are the official CVE record's own, retrieved 2026-10-25 from NVD. Category, attack surface and cross-links are this registry's classification and can be wrong — use the button above. Not a severity assessment for your deployment.