PT-2026-65888 · Rubygems · Mcp

CVE-2026-63118

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Published

2026-07-29

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Updated

2026-07-30

CVSS v4.0

6.9

Medium

VectorAV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
Name of the Vulnerable Software and Affected Versions mcp versions prior to 0.23.0
Description The MCP::Server::Transports::StreamableHTTPTransport component in the mcp gem fails to validate the HTTP Host or Origin request headers. This allows a malicious browser page to utilize DNS rebinding—a technique used to bypass the Same-Origin Policy—to access a locally running MCP server and invoke its exposed tools.
Recommendations Update to version 0.23.0.

Exploit

Fix

Origin Validation Error

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Weakness Enumeration

CWE-350CWE-346

Related Identifiers

CVE-2026-63118
GHSA-RJR6-RCGV-9M7M

Affected Products

Mcp