cve.bz

CVE-2026-34742

7.6 highEPSS 0.5%

High (7.6) in lfprojects mcp go sdk. EPSS 0.5% chance of exploitation in the next 30 days. Fixed in github.com/modelcontextprotocol/go-sdk 1.4.0.

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.

Severity

CVSS 4.0

7.6 high
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

8.1 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS
0.5% chance of exploitation in the next 30 days; higher than 40% of CVEs (scores of 2026-10-31)
CWE
CWE-1188
Published
Modified
Record from
the NVD, synced

Affected

Packages (OSV)

AdvisoryEcosystemPackageAffectedFixed in
GHSA-xw59-hvm2-8pj6Gogithub.com/modelcontextprotocol/go-sdk<1.4.01.4.0
GO-2026-5771Gogithub.com/modelcontextprotocol/go-sdk<1.4.01.4.0

References

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