CVE-2026-67432: high-severity vulnerability in modelcontextprotocol ruby-sdk
MCP Ruby SDK: Unbounded JSON-RPC request body causes uncontrolled memory allocation in StreamableHTTPTransport
Published
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.8%
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 reads and parses an entire JSON-RPC POST body without a size limit, allowing an unauthenticated remote attacker to exhaust process memory. This issue is fixed in version 0.23.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
modelcontextprotocol · ruby-sdkRelated CVEs — modelcontextprotocol ruby-sdk
In the same product, most dangerous first.
CVE-2026-33946HIGHMCP Ruby SDK: Insufficient Session Binding Allows SSE Stream Hijacking via Session ID ReplayEPSS 0.5%CVE-2026-67430MEDIUMMCP Ruby SDK: Unbounded session retention in StreamableHTTPTransport allows memory exhaustion via initialize floodEPSS 0.4%CVE-2026-67431HIGHMCP Ruby SDK: Ruby SSE Session PoisoningEPSS 0.4%CVE-2026-63118MEDIUMMCP Ruby SDK: Streamable HTTP transport lacks DNS-rebinding (Host/Origin) protectionEPSS 0.2%CVE-2026-63119MEDIUMMCP Ruby SDK: Unbounded line buffer in stdio transports leads to memory exhaustion (DoS)EPSS 0.2%