CVE-2026-34742
HIGHModel Context Protocol Go SDK: DNS Rebinding Protection Disabled by Default for Servers Running on Localhost
Title source: cnaDescription
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.
Scores
CVSS v3
8.1
EPSS
0.0007
EPSS Percentile
22.1%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
total
Details
CWE
CWE-1188
Status
published
Products (3)
lfprojects/mcp_go_sdk
< 1.4.0
modelcontextprotocol/go-sdk
0 - 1.4.0Go
modelcontextprotocol/go-sdk
< 1.4.0
Published
Apr 02, 2026
Tracked Since
Apr 03, 2026