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.

The remote Fedora 44 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2026-8b0a672383 advisory.

    Update to 1.91.0

    ----

    Update to 1.90.0

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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.
    (CVE-2026-34742)

ID	Name	Product	Family	Severity
310680	Fedora 44 : glab (2026-8b0a672383)	Nessus	Fedora Local Security Checks	high
439672	SCA: security update for github.com/modelcontextprotocol/go-sdk (GHSA-xw59-hvm2-8pj6)	Tenable Cloud Security	SCA Checks	high
439672	SCA: security update for github.com/modelcontextprotocol/go-sdk (GHSA-xw59-hvm2-8pj6)	Tenable Self-Hosted Container Security	SCA Checks	high

Detections

Analytics

CVE-2026-34742

high

Tenable Plugins

high

high

high