CVE-2026-63118

Severity CVSS v4.0:

MEDIUM

Type:

Unavailable / Other

Publication date:

29/07/2026

Last modified:

29/07/2026

Description

MCP Ruby SDK is the official Ruby SDK for Model Context Protocol servers and clients. Prior to 0.23.0, MCP::Server::Transports::StreamableHTTPTransport in the mcp gem does not validate the HTTP Host or Origin request headers, which allows a malicious browser page to use DNS rebinding to reach a locally running MCP server and invoke exposed tools. This issue is fixed in version 0.23.0.

Impact

Vector 4.0

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N CVSS v4.0 Severity and Metrics:

Base Score: 6.90 MEDIUM
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

Attack Vector (AV): Network
Attack Complexity (AC): Low
Attack Requirements (AT): Present
Privileges Required (PR): None
User Interaction (UI): Active
Confidentiality (VC): High
Integrity (VI): None
Availability (VA): None
Confidentiality (SC): High
Integrity (SI): None
Availability (SA): None

Base Score 4.0

6.90

Severity 4.0

MEDIUM

CVE-2026-63118

Description

Impact

References to Advisories, Solutions, and Tools