CVE-2026-34742

The record

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 packages

Related vulnerabilities

• CVE-2026-87827 Certain KGUARD DVR devices running vulnerable firmware expose a system command execution… CWE-1188
• CVE-2026-86464 In the current development version of Eclipse aeriOS, for which no official release has… CWE-1188
• CVE-2026-77348 Wallos is an open-source, self-hostable personal subscription tracker. CWE-1188
• CVE-2026-53507 oasdiff-action is a GitHub Action that detects breaking changes in OpenAPI specs and post… CWE-1188
• CVE-2026-75062 Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') in… CWE-1188
• CVE-2026-55581 mcp-shell is an MCP server for running shell commands securely, auditably, and on demand. CWE-1188
• CVE-2026-62388 NLTK versions before 3.10.0 default to ENFORCE=False in pathsec.py, causing all security… CWE-1188
• CVE-2026-33921 The Windows installer deployed Npcap leaving its access restriction option at the… CWE-1188